"STAB" stands for "same-type attack bonus", and it means that you get more damage for using a move of the same type as your pokemon. Go in fact scales down the STAB effect from the main games to a 1.25x bonus (in the main games you get a 1.5x damage bonus for using a move of the same type), but it's arguably in many cases more relevant in Go, given the limited movepool, the inability to choose moves besides choosing the pokemon they're found on, and the fact that weakness, resistance, and immunity are scaled down even more sharply to be of the same effect.
What is "w/ stab"?
I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

I have noticed that Pokemon can have moves that are more powerful w/ stab and I was wondering what it was and how can I know one of my Pokemon has it with their moves?
Here are Tentacool's moves as an example.

Answers
Hey GofessorOak, thanks for the clarification.
Does STAB stack with weaknesses too?
To use the Tentacruel example, Tentacruel is a Poison/Water type Pokemon, so any Poison/Water attack I use gets the STAB bonus (17.86/dps w/ Poison Jab). Does that also increase if I was fighting say a Venusaur which is a grass type Pokemon that is weak to Poison types?
If it does stack, that would mean I would really be doing 22.33/dps with my Poison Jab because of the x1.25 weakness bonus against Grass types. Am I correct on this? This would drastically change how I challenge rival gyms.
Thanks!
Venusaur is in fact not weak to Poison moves as it is also a Poison type which resists Poison (in this case, 1.25 .8 cancels out, although, yes, STAB figures on top of weakness and resistance, the attack does 1.25x damage). Now, if Venusaur attacks Tangela (the only pure-grass in Gen 1 I think) with a poison move, the move is doing 11.25*1.25x damage, or 1.525x.
A note, Pokemon Go does not have double-type weakness or resistance. In the main games, Charizard would take 4x damage from Rock moves and 6x from STAB Rock moves, while Venusaur would take .25x damage from Grass moves and .375 if those attacks were STAB'ed. This game also treats type-based immunity (i.e., Flying taking most Ground moves 0x besides one unique to Zygarde or in the constraint of Gravity) in the main games as only a resistance, so Charizard/Zubat/Aerodactyl/Zapdos/Moltres might take Ground moves 1x in Go though 0x in the main games.
How do you know that double weaknesses do not stack? Why shouldn't a Cloyster with Blizzard to the following to a Dragonite:
1 * 1,25 (Dragon weak to Ice) * 1,25 (Flying weak to Ice) * 1,25 (STAB) = 1,95.
Thanks for clarifying!
P.S.: In this reddit people confirmed that double resistances stack. https://www.reddit.com/r/TheSilphRoad/comments/4tkize/resistance_stacking_works_as_expected/