Currency for this website. People use it to trade for art, signatures, in-game items, in-game bells, etc, but it's on-site purpose it to buy collectibles to display under your avatar. If you click on shop at the top of the site you can buy collectibles, and store you bells in the ABD (bank, basically). It's only purpose is to hide your amount from other users, since interest has been disabled.
& the going rate for TBT = in-game bells is anywhere from 5-10 million in-game bells per 100 TBT bells