IV: IV refers to Individual Values. This is the basic statistic of each Pokemon. Each Pokemon has three statistics: Attack, Defense, and HP. All three can range from a low of 0 and a high of 15. A Pokemon with a 15/15/15 stat is considered as having a perfect IV. The only time the IV of a Pokemon may change is when that Pokemon is traded. Since a Pokemon can only get traded once, there is only one IV change per Pokemon in its lifetime.
Meta: When people say, “this Pokemon is part of the meta,” they are referring to the fact that this Pokemon has a good win rate against the rest of the Pokemons in that particular Go Battle league, and hence are often used by top trainers.
PvE: Player vs Environment. This refers to raid battles or Team Go Rocket battles.
PvP: Player vs Player. This refers to either Go Battle League battles or trainer battles.
Type Effectiveness: Different Pokemon have different types. Some Pokemons have one type, while others may have two different types. Certain types of Pokemon are stronger against other types. For example, water-type Pokemon are effective against fire-type Pokemon. You can view a type effectiveness chart here.