Agree that it could be clearer. The idea of the '?' is to let you enter a location without the hassle of having to save it first. Useful for times when you want to go someplace, but it's not common enough to warrant saving it
To me, it seems like this (the ? ) is the strongest feature of the app. My kneejerk reaction is that if you go to a place often enough to save it, you probably don't need directons anyway (or won't after one or two trips).
Nitpick aside, this is a beautifully simple interface.
I would guess that the most common use case is getting from the current location to a new destination (?). What if those 2 were more prominent? Saved locations could be an additional option but to make this more efficient, I would bring those 2 options to the forefront.
Also, I'm not sure what "?" is. I assume that it lets you enter an address, but it's best if I don't have to try it to figure it out.