We Just got one at a local Target. Instructions on how to use the Bakugan Trap is posted already in the News Segment on Bakugan.com.
It needs to be used together with a marble of the same color. The trap will help you change the attribute of the marble in play or add more G points to it.
So it depends on your luck when you buy a trap, it may have G points or a complementary attribute. It only have meaning when you turn over the card in play.