A drive is a computer hardware component that reads and writes data on discs. Hard drives store data magnetically whereas optical drives use a laser, guided by an optical lens installed within the drive, to read and write data in digital format.
CD-ROM and DVD-ROM drives can only read data from CD-ROMs and DVD-ROMs, whereas CD-R and DVD-R drives read as well as write media on discs like CD-Rs and DVD-Rs. CD-RW drives and DVD-RW drives can erase and write new information on CD-RW and DVD-RW discs.
Lenses in optical drives focus laser beams on the disc that heat its surface to form pits. The level space between pits is known as land. When a laser beam strikes a disc, diffuse light reflected from pits is read as "1," whereas the sharp beam of light reflected from land is read as "0" by the computer. Rewritable drives erase data on rewritable discs by heating them to temperatures lower than that used while writing data.
Optical drives spin discs at a much slower rate than hard drives. However, optical drives are popular, because optical media is inexpensive, easily transportable and secure.