Question about fold equity.

[Duffman]

I'm slowly starting to understand the concept of Pot Equity.
As far as I understand it is the percent chance I have to end up the winner, and if it is larger than the average equity(100 divided by the amount of people in the hand) then I should bet, or push my edge in another way.

Now is fold equity the equity I gain by other people folding, or is it the equity I gain if I fold?

If it is the equity I gain by folding then can someone explain to me how exactly that works? I thought that a fold is always 0% equity.

Sorry my post isn't clear, I'm pretty stoned.