I've read the pages about ev training and I still don't understand.
revise on this:http://Pokemondb.net/ev
EV training is all about achieving stronger Pokemon,you can ev train and gain a bonus 31 IVs (stats) if you EV train for a peticular stat,then you can hit harder,defend harder and go first,they are useful.
If you still don`t know you can ask me.
Read this if you have not already:
If you still don't understand, comment and I will explain myself as I have plenty of experience in EV training.