Basically the game is like The Sims, except rather than controlling your characters in a environment where you only interact with the computer, you're actually interacting with real people. It's free to sign up and create a character, but you need to pay money if you want to own land, open a business, etc. It's like real life, but on a virtual world. Oh Tad Williams, how right you are (if you don't know Tad Williams, look up his Otherland series).
