DVD ("Digital Versatile Disc" or "Digital Video Disc") is a popular optical disc storage media format that can be used for data storage, including movies with high video and audio quality. DVDs is modelled in size after the compact disc (i.e. diameter: 120 mm or 4.72 in, occasionally 80 mm or 3.15 in.); both are optical storage media so similar that a DVD reader or writer can usually read CDs, but DVDs are encoded in a different format of much greater density, allowing a data storage capacity 8 times greater (single-layer, single-sided).
All read-only DVD discs, regardless of type, are DVD-ROM discs. This includes replicated (factory pressed), recorded (burned), video, audio, and data DVDs. A DVD with properly formatted and structured video content is a DVD-Video disc. DVDs with properly formatted and structured audio content are DVD-Audio discs. Everything else, (including other types of DVD discs with video content) is referred to as a DVD-Data disc. Consumers use the term "DVD-ROM" to refer to pressed data discs only, but that is incorrect usage; moreover, the term DVD is also applied generically in describing newer video disc formats, Blu-ray Disc and HD DVD.