A bizarre and successful marriage of the tv quiz show and improv comedy, to create a replacement for tv's sitcom.
As with most new tv show formats, it was copied to death after the first successful examples appeared (in this case, in the UK):
(There are others, such as It's Only TV But I Like It, or Channel 5's little-watched quizcom covering science fiction).
Pretty much, the format is a quiz, with a stand-up comic as quiz master, another stand-up comic as one of the two team captains, and a topic expert as the other team captain.
The focus of the tv programme, (unlike most tv quizzes), is not on which team wins but instead on how they play the game.
The question's provide a means by which savvy team members can get cheap laughs, easy laughs or, remarkably often, really good one-liners on-screen.