What is a "troll question", and how do you know when you've come across one for sure?

In Internet slang, a troll is someone who posts inflammatory, extraneous, or off-topic messages in an online community, such as an online discussion forum, chat room, blog, or in this case Yahoo Answers, with the primary intent of provoking readers into an emotional response or of otherwise disrupting normal on-topic discussion. Basically in lamest terms, they are dumbasses.