Like when you have 7xBB in a tournament, and push into a high stack with 100xBB. He will call with a wide range of hands, so therefore your fold equity is bad.

Fold equity = Ability to make the opponent fold.

Also, if you get to a river after firing two barrells, the pot is $52, and the villain has $10 left, you have almost no fold equity left. He's going to showdown most likely.