I saw it on the info for cresselia, and I guess that you put it on every pokemon, but what is it.
It shows what EVs, or effort values you get from each pokemon. Like typhlosion's EV yield is three special attack points, so if I KO a typhlosion, my pokemon will get three special attack EVs.
You can either go to the pokemon's pokedex entry or look here to see them all: http://pokemondb.net/ev/all
