???

These marks can be found all across Vana'diel in varying locations. They don't share any common purpose - they're just special "hidden" spots that are used for different quests, missions, spawn points, etc. Sometimes you'll need to trade an item to one of these ??? and other times you can just click on it.

It may not be wise to randomly click on any ??? that you find, either. Some will spawn very hard monsters that you may not be ready to take on! But of sourse...if there's a button, there aren't many who can resist testing it...