Why is Who's On First so funny?

Who's On First is funny because what the guy is asking is the name of the players. Who was on first, seems like a question, but it was an answer. What is the guy's name on second, again, sounds like a question, but an answer. Third base and shortstop are also sounding like a question, but they were an answer. Third base was I don't know, and shortstop was I don't care. Plus, the actors try to make it funnier in a way, and it has seemed to work.