most tanks are merely juice holder/feeders for your cartomizer. The carto goes inside the tank. The advantage of a tank is that it keeps feeding the carto through holes or slot(s), thereby always keeping it soaking wet and hitting hard...plus you don't have to keep topping the carto off after 20 or 30 hits... The life of your carto will generally be longer as well because of the avoidance of dry hits and possible burning of the filler material. There are some tanks (in the minority) that feed their own built in atty through built in wicks...many argue that these do not feed the juice at a rate of speed that keeps up with their vaping.
duplicious?...if you meant to say that, it's pretty funny..kind of like doubly delicious? If you didn't mean to say it...well congratulations anyway on making up a great word..