A hard disk (or hard drive) is internal hardware which stores and provides access to large amounts of information. Most new computers include an internal hard disk that contains several gigabytes of storage capacity.
Magnetic platters, electronics and mechanics make up a hard disk. The platters are fixed to a spindle. On each side of a platter there is a read/write head. Each platter is divided in to tracks, which again is divided into sectors. A characteristic with hard disks is that the platters and the mechanics are in an airtight enclosure, and that the read/write heads do not touch the platters as long as the platters are rotating.