It is pretty much the same as Ctrl+Tab but with more options (see attached pic). Using Ctrl+Tab you cycle around the open drawings without really knowing what drawings you have open.
With this you can click on the drawing you need to access immediately. This tool is excellent when you have multiple xref drawings into one, so when you need to edit one drawing you just "choose drawing - edit and save - click host drawing tab - update/save xrefs".