What is a DVD?

DVDs are a form of optical storage media based on the compact disc. Originally called Digital Video Disc, and later Digital Versatile Disc, "DVD" is now used with little sense of the original terms. Essentially, a DVD is a larger, faster CD that can hold video, audio, and/or computer data. Physically similar to a CD, a single-layer, single-sided DVD has a maximum capacity of 4.7GB (about two hours of MPEG-2 video), about seven times the capacity of a CD-ROM (a normal CD holds around 650MB). A double-layer, double-sided DVD-ROM disk has thirty times the capacity of a CD-ROM (over 17GB). The DVD specification supports access rates of 600KBps to 1.3MBps.

DVD-ROM describes DVDs used as computer storage. DVD-R is a once-recordable DVD format, which requires a special drive and media, while such formats as DVD-RAM, DVD-RW, and DVD-R/RW can be written multiple times.

DVD-ROM players are capable of reading CD-ROMs, CD-I disks, and video CDs, as well as new DVD-ROMs. Most DVD players can also read CD-R disks.

For more information about DVDs, see the online DVD FAQ.

Also see:

• What are bits, bytes, and other units of measure for digital information?
• In Mac OS, how are CDs usually formatted?
• How can I find out what kind of CD-ROM drive I have?
• What is Blu-ray?