IV's are the values each Pokémon has that makes Pokémon of the same specie different. Those are always between 0 and 31 on each stat. 31 is the highest possible. EV's are the points Pokémon gain from battaling others and each Pokémon can gain 510 ev's at a max of 252 each stat. Each 4 ev's raise the stat by 1 point what means that 252 ev's will raise the stat by 63 points. You can only max 2 stats and add a point to other. 252+252+6=510.