The carto IS the atty -- it has an atomizer within the tube. You then put that inside the glass tank, making it a cartotank. They are a different animal from a clearo, a vivi nova is a type of clearo. A clearo is plastic and uses a silica wick. I don't like plastic, I don't like silica = I don't like clearos. I do like glass, I do like metal atties = I like cartotanks. The disposable part of a cartotank is the cartomizer itself that holds the atty and is the part that you punch the hole in to let the juice in.
Cartomizers were originally used alone and you filled them with your juice. The Blu and the other cig-a-likes still use them. If they got dry, the filler would burn and you had to throw them out, plus if they got dry the atty in them would fail. Someone much brighter than I decided that if they punch a hole in them and put them in a tank, it will self fill and thus not get dry. With them encased in a tank, they stay wet and will last longer. Mine don't usually burn out, I just start getting a hard draw and they need cleaning out. Some people toss them at this point since they are a buck a piece; some people clean them. I still have filler for them but never got good at replacing the filler