Reddit is a wildly popular social media community, in which users share links and comments. In an AMA session, one person fields questions from the community. A variety of noteworthy people have taken part in these sessions, including Steve Colbert, Jimmy Kimmel, and “Jeopardy” champion Ken Jennings.

Around 4 p.m. ET, Obama tweeted that he would be taking questions online starting at 4:30. White House Press Secretary Jay Carney even tweeted a photo of the president sitting in front of computer, presumably scanning the questions. Shortly after the session began, however, users began complaining that they couldn’t access the site because of the high volume of activity.

So how much do you know about Reddit? Here are 10 facts and figures to serve as a crash course:

Reddit was founded in 2005 by two University of Virginia graduates Steve Huffman and Alexis Ohanian.