A Cartomizer is a small diameter metal cylinder with a coil placed inside of it that is encased in filler material to hold/absorb
juice so that the coil can vaporize it. If/when the fluid level gets too low, the filler material burns and forever gives an awful flavor - its dead. A clearomizer is a tank that hold
juice around a coil that has wicks placed in it to absorb the
juice. The wicks are typically silica that absorb juice and make it available for the coils to vaporize. Silica typically doesn't burn. So, if the juice level in the tank gets to low for the wicks to pick up, you get a bad/burnt flavor. But, re-fill the tank, and you are able to continue with normal use. Some (myself included) find that the flavor of even undamaged filler material in cartomizers taints the flavor of the juice where clearomizers don't. Others say that clearomizers mute the flavor of juice. YMMV.