the one on the left is your black tank flush, when dumping you can connect a nonpotable hose to it and rinse out your black tank.
the one on the right is just as you say, an outside water outlet for washing, watering your flowers etc. kinda nice to have since you do not need to disconnect your city water to get a hose hooked up.
there is a inside valve to shut it off for cold weather, just like a house would have.
mine is near my water pump in the hall closet.
you call them ferrets, i call them weasels.