sorry if i don't give you enough information :/
well, i watched this video a while ago for EV training help.
http://www.youtube.com/watch#playnext=1&playnext_from=TL&videos=-O7J7r5YYWk&v=EIUPhmaklOI
basically, when you defeat a pokemon, you gain EXP, but you also recieve something called EV points, which are hidden(you can't see them)
ev, or effort value's are received along with exp. these ev points can help your
pokemon greatly, as they can raise your stat gains dramatically when you level up.