It's a 3d virtual world. Used to have a sim on there that did live podcasts from a 'stage' with a live chat (Rantradio if it rings a bell).

I also spent evenings nannying a friend's kid and did ad offers on there for awhile which is how I generated the $20. It is redeemable for fiat but the process of getting it into Bitcoin was non trivial at the time, and I didn't have a checking account.