It's a documentary by Bill Maher, it's hysterically funny, and very true. If you're hardcore religious I wouldn't recommend seeing it, as it's pretty offensive to all forms of religion. An atheist like myself thoroughly enjoyed it. In fact, I thought it was the best documentary I'd ever seen in my entire life and I watched it a second time.
It looked funny, but I never got a chance to see it. And that type of movie is officially known as a Mockumentary.
Actually, when I think of mockumentary, I think of The Office (i.e. fake). It's more of a satire. Edit: And on that note, see it.
I actually didn't unfortunately get to see the whole thing :/ But from what I saw, I thought it was excellent. XD
It was fairly amusing, albeit a bit short. He could have definitely done a lot more with it than he did.