Toner: The fine black powdered ink used to print text and images.
Drum: The device used to transfer the toner to the paper (creates the image).
The Drum is the more expensive part, so it is recommended to purchase a printer where the Toner and Drum are separate.
Eg: If you print 15,000 pages a year, the difference in cost between the two printers in consumables (toner) is