What does EV or IV stand for in Pokemon?
It means the Pokemon was trained in certain stats.
Battling Pokemon gives you a certain amount of EV points. For
example, battling a starly gives you 1 speed EV point for the
Pokemon that battled it. Different Pokemon give different EV's.
EV's work like the following:
every 4 EV's you get in one stat, that stat is raised by 1. The
maximum EV's you can have in any one stat is 255 and the total
number of EV's your Pokemon can have is 510. So essentially, only
two stats can be fully maxed. You could also divide up the EV's
evenly into the stats, but that's not the best thing to do.
EV-training is tedious, and without the right items, it takes
forever.
Go to serebii.net for all the info about EV's.