The term was used almost exclusively by Apple as a name for the low-end substitute for their high-end SuperDrive, as the latter was designed to both read and write CD and DVD recordable media.
The device was created as a mid-range option between a CD burner and a DVD burner, which at the time the combo drive was introduced was generally an expensive option costing in excess of US$300 a unit.
Combo drives are becoming less and less common on new systems, though they do occasionally appear in lieu of CD-only drives on low-end computers and business computers to lower production and sale costs.
The cost difference between a combo drive and DVD burner has been steadily declining in recent years, so most new PCs (except for the low-end budget computers) have a DVD burner (which also reads and writes CDs).
As of October 2008, the MacBook comes with a SuperDrive as standard, and as of March 2009, the Mac mini comes with a SuperDrive as opposed to the usual combo drive.