In my experience it's mostly a venue for people to buy and decorate their own digital homes and avatars, and just hang out and talk. SecondLife is a giant archipelago of (infinite?) islands, you can either teleport or just fly between them, and many of them have various degrees of elaborate landscape architecture, shopping malls, and clubs. I just logged in last night after leaving that comment to check in on my old toon and everything is basically the same.
