If this is for post adv then Pokemon can receive a
total of 512 evs and a total of 255 evs for each stat. Everytime you beat a Pokemon you will receive from 1 to 3 EVs in one or two stats. The number of EVs you get and the stat(s) the EV(s) apply to
are determined by the specie of the Pokemon. At level 100, for each 4 EVs, the stat will be 1 point higher. (at level 50 for each 8 etc)
IV's are easy. They are a value from 0 to 31, different for each Pokemon and stat, and inherent to the Pokemon. If say, a level 100 Charizard (assuming neutral nature) with 0 Attack IV has 198 attack, had the same charizard had an attack IV of 31, it's stat would've been 229. The variation of the stat due to the IV is proportional to the level of the pokemon (like with the evs)