I've read the pages about ev training and I still don't understand.
http://Pokemon.marriland.com/black_white/how_to_ev_train http://www.psypokes.com/labhttp:/ http://www.serebii.net/games/evs.shtml http://www.smogon.com/bw/articles/bw_ev revise on this:http://Pokemondb.net/ev http://bulbapedia.bulbagarden.net/wiki/Effort_values http://naruto.viz.com/forum/showthread.php?t=25028 http://www.friendcodes.com/forums/5th-generation/184870.htm
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:
http://Pokemondb.net/ev
If you still don't understand, comment and I will explain myself as I have plenty of experience in EV training.