Fold equity

[MuckerFish]

Could someone please provide a brief description of the concept of fold equity for me. I see it come up alot and I don't completly understand. Let me interrupt those of you who are currently replying with the "Do a f*@%ing search" type thing to let you know I already did and because it contains the words fold + equity just about every post on the boards pops up in the results. I just could'nt find a good definition.

Thanks in advance!