"Q"

I just came across an article about the theory of "Q". I don't really recall ever hearing about it, but it does sound familiar. It's really interestin and if any of you know more about it please tell me. If you, like myself 5 minutes ago, have no idea what "Q" is, let me fill you in. "Q", which stands for Quelle (german for source), is a hypothetical book that provides an explination to the parallels in Matthew and Luke that are not present in Mark. It's all very interesting. I'm hungry for more information, so if you've got it hand it over.