CD-ROM is the name of a type of optical media. It consists of a compact disc containing read-only memory.
Similar in structure and appearance to audio CD's, CD-ROMs are a standardized 12 cm wide, and employ a 780 nm laser. This light is broader than that used by latter optical media, but is still small enough to give CD-ROMs up to a gigabyte capacity, depending on the model. The standard transfer speed is about 150 KB a second, but some drives are capable of reading information over 50 times quicker.
The technology behind the CD-ROM was first developed in the 1970's by Phillips and Sony. However, the technology was not introduced to the general public until 1985. Many video game makers quickly became interested in the potential of the format, since it held far more data than the standard cartridges of the time. Nintendo in particular sought a contract with Sony, in which the two companies would unite to create a game system called the "PlayStation" using CD-ROM technology. However, Nintendo backed out of the deal at last minute, instead opting for a partnership with Phillips and, eventually, forgoing the use of CD-ROMs in general for their Nintendo 64 system.
Sega, on the other hand, eagerly adopted the new technology, incorporating it into the Genesis add-on the "Mega-CD" and eventually into the Saturn. many third party developers would come to support Sega over Nintendo for this very reason, since the CD-ROM gave them the space to create more complex games, despite the Saturn's limitations.
Although still used as an audio format, CD-ROM technology was largely abandoned by console manufacturers by the 2000's. Instead, more advanced forms of optical media were used, including the Mini-DVD and the GD-ROM.