it is telling you where you are in relation to an undiscovered region. if you've discovered it, it would say "South of Paludes Sechhi" or something like that, with a name instead of "???"
when it's "???" you head the opposite direction it says on the compass bit, and you'll find it.
and currently the only way to find regions you haven't explored is to make a personal map, which would take a l ot of time and resources.