What: Yedda, which is both a question and answer forum and a social network. People. Sharing. Knowledge.
When: Some years back. I'm sure you could find out by doing a general Internet search. Just put 'Yedda' in the search line.
Who: Again, that will be available on the 'Net. I believe the founders (Yaniv is one) are based in Israel, which is where Yedda's staff is based though Yedda is now owned by AOL.
Why: Why not? There was nothing out there quite like Yedda, so it seemed like an idea whose time had come.
Where: Everywhere, of course. Yedda has members from all over the world.
Anything else we can do to help?