Clearomizer is like a cartomizer without the polyfill. Cartomizer tank set up is basically a cartomizer with a hole punched in it within a tank that acts as a resevoir and an ego tank is a nice concept that I never got to function consistenently enough but is basically supposed to be like direct dripping with out having to manually drip (a little tank on top of an attomizer). I hope this helps.
What he said. A tank is a reservoir for juice that you put a cartomizer in with a hole punched in it that vaporizes your juice. A clearomizer is usually a one piece unit that has the reservoir and the atomizer all in one piece that vaprizes your juice. The lines are getting a little blurred with the new products. I consider it a tank when it doesn't come with an atomizer or cartomizer and a clearomizer is ready to vape out of the box, or at least you hope so. Good luck!
As DCB said, the clearomizer is just a Carto without the stuffing, it generally works without a lot of hassle (not firing, leaking and such) and once it get's funky it's thrown away unless you want to try and re-wick it. A tank uses a carto and hold a lot of juice, the carto can be pretty much any brand/resistance you want as long as it fits the tank design (some carto's have a larger diameter than others and can't be used in some tanks). Once the carto get's nasty you drain your tank or vape until empty then take it apart and throw the carto away and replace with a fresh one that is punched or slotted. Some tanks are a royal pain while others are a joy to use. A year ago we had Cart's, Carto's and Atty's, now we have DCA's, Tanks, Bottom Feeders, Clearomizers, XL Caromizers, Blow your mind Atty's and any number of new idea's that are coming out almost daily.
A tank holds a cartomizer with a hole punched in it. The cartomizer is a heating coil surrounded by heat resistant wicking material that keeps the coil wet the majority of the time. A clearomizers heating coil is located at the top with a rope like wicking material that needs to be submerged in the liquid, kind of like a zippo wick. Both have their pros and cons, but the clearomizers are not for chain/heavy vapors due to the fact that the wick needs time to absorb. Cartomizers are easier to keep saturated in a tank set up because the liquid is drawn into the wicking material with suction when you draw on the mouthpiece. I have never gotten a clearomizer to work efficiently. If you PM me your info, I'll send you a clearomizer to try out for free, I have a spare one that I never used.