Super Single (is what its usually referred to as) is where instead of keeping the truck moving 24/7, you each drive for 8 and sleep for 8.
Advantages and disadvantages should be fairly obvious. Advantages...you get a chance to sleep without the truck moving, you get time with your spouse. Disadvantage, you get to sleep without the truck moving ($$$), and you get time with your spouse.
(kidding, of course)