The conceit is simple. The site presents pictures of "real" amateur women in banal everyday situations. Click on a "reveal" button, and a naked, highly explicit picture of that same woman suddenly pops up.
The central gag is that it's almost impossible to guess her muff. Take that reserved, chubby accountant you pass on your way to the shitter every morning... yeah, turns out she's shaved, pierced, and has a distinct penchant for dongs.