TBT is a double-short ETF on Treasuries 20-years and longer. It is a double-inverse of TLT. As those longer-dated Treasuries prices fall (thus their yields go up), TBT goes up.
There are even more leveraged inverse ETFs like triple-short 10-year Treasury (TYO) and triple-short 30-year Treasury (TMV) but they are very thinly traded for my liking.
It looks like I've missed the boat on this, but I think there's still some upside left on this leg. It can run up to $55 or so (target price derived from the height of the symmetrical triangle), where it meets a horizontal line that marks the previous resistance/support.
What's interesting to me is that TBT broke out and continues to go up, DESPITE the dollar strength (take a look at the top of the chart - that's US dollar movement). So, as I mentioned in the post a few days ago, the U.S. dollar "strength" doesn't mean investors are flocking to the U.S. dollar denominated "safety" assets like Treasuries. It is rather other currencies' weakness.