What are IV's in pokemon d/p and what are they for and how do i earn/get them?

Answer 1

IV stands for Individual Value. Individual values are randomly added onto your pokemon's base stats and are the cause of variation in stats between pokemon. Your pokemon's IV's are set from the first time you see them, and in a few cases such as some legendaries they are set when you start the game. You cannot change a pokemon's IV's, just like you cannot change its nature or its poffin preferences.

Answer 2

serebii does a good job of explaining it, evs are more important though
http://www.serebii.net/index2.shtml