What are IVs?

Pokemon have 2 sets of stats, base stats which are determined by specie, and Individual Value (IV) which can range from 0-15 and are added to the base stats. The IV is used as a way to evaluate the strength of a Pokemon within a specie. Usually ppl use IV as percentage which is the % of perfect IV. You can look in this guide for more details:
https://pokemongo.gamepress.gg/pokemon-stats