This forum curency, commonly known as TBT,
or more appropriately, BTB (
Bell
Tree
Bells) can be used for a lot of things.
Here's an official Sticky Thread that should be
very helpful in answering most of your questions:
(how to earn them / where to use them, etc)
http://www.belltreeforums.com/showthread.php?64715-The-Bell-System-Beginner-s-Guide
and if you look at the sidebar on your left, under your user name & avatar,
you should see a section that says: "Bells"
You currently have 1,018.
If you need to send / receive these forum bells to/from other users,
you can click on that "Bells" section, and a pop up menu will let you enter the amount, notes and so forth.
Both parties will receive an instant notification right away regarding your transaction.
Really handy.
(You can also go to the upper right corner and click on that "currency" section to transfer these Bells, but you have to select/enter the correct name from there.)
Hope this helps! C: