A peripheral device that allows a computer to read or/or write some storage medium such as a hard disk, floppy disk, magnetic tape, compact disc or DVD. These would be called a disk drive, magnetic tape drive, etc. CD and DVD drives are known collectively as optical drives. When unqualified the term probably refers to a hard disk drive.
Of the above storage media, typically only hard disks are fixed, the rest being removable. Most PCs in 2009 include one disk drive and one optical drive housed in the main PC enclosure. Extra drives can be connected externally via USB, SCSI or Firewire. Magnetic tape is always removable and tape drives are typically external.