But how does sending and receiving your email and other messages through Facebook actually work? Most consumers will have to wait a few months for an invite to try out the new Facebook Messages system, but we were lucky enough to snag to take the service for a test drive. Brave the sights and sounds of downtown San Francisco to see PCWorld editor Mark Sullivan's guided tour of the new Facebook Messages interface, including a first look at features like SMS messaging and the automatic filtering at work in your "social inbox."