OU - Overused
UU - Underused
NU - Neverused
EV- Effort Value
IV - Internal Value (?)
6x31 - A pokemon with 31 in every IV
GTL - Global Trade Link
Comps - Pokemon with natures, IVs, and movesets determined to be good for competitive play
LF - Looking for
Ubers, OU, UU, and NU are tiers for competitive play
EVs and IVs determine a Pokemon's stats