Clearomizers are disposable containers for your e-liquid. These have wicks in them that will eventually burn away, so you won’t get as good a vape. These need to be replaced.
Coils, by comparison, can be changed, so that the tank (the container for your eliquid) can be reused again and again.
Cartomizers, however, are disposable. Once the liquid has run out, the cartomizer (or pod) cannot be reused.