It's bell forums money basically so you see how under your name or mine it says BELLS:131 under yours that's how many TBT yiu have currently so let's say you enter a bid for something you can bid 100tbt all yiu have to do is click where it says bells under that persons name enter the amount and transfer that amount to them in order to obtain your villager. TBT is an easier faster way of doing trades rather than the traditional method of dropping bells or retail