In Gen 1-2 Pokemon Got EV's To the stats they have.
In Gen 3-5 Pokemon Get EV's Compared to the EV-Thingy they have chosen.
In Gen 1-2 Pokemon Have IV's Be Like All Shiny Pokemon Can't get too much different IV's.
In Gen 3-5 Pokemon Have IV's Be not changing the Shiny-Pokemon-Thing.
A Pokemon Can Have A Total of 31 IV's in each stat. (Gen 1-5)
A Pokemon Can Have A Total of 255 EV's in 1 stat, and 510 Total in all Stats (Gen 3-5)
A Pokemon Can Have A Total of 65535 Ev's in Every Stat. (Gen 1-2)
A Pokemon Gets 1 More Point in a Stat For Every 4th EV's it Gets. (Gen 3-5)
A Pokemon Gets 1 More Point in a Stat For Every 1 IV's it Gets. (Gen 1-5)