It’s an indicator of the relative strength of the USD. It’s worth noting that while it’s lower then a few moths ago, it’s higher then it was a year ago. IOW the USD is still stronger then it was before the Lehman collapse and financial market seize-up.
In the bigger picture, the USD has been in a long term decline since about 2000, that temporally reversed itself during the financial crisis, but it’s now reverting to that longer term trend. (Unless I'm mistaken this particualr metric doesn't go back that far.)