The following is from the PC Webopaedia (http://webopedia.internet.com/TERM/D/DVD.html):

Short for digital versatile disc or digital video disc, a new type of CD-ROM that holds a minimum of 4.7GB (gigabytes), enough for a full-length movie. Many experts believe that DVD disks, called DVD-ROMs, will eventually replace CD-ROMs, as well as VHS video cassettes and laser discs.

The DVD specification supports disks with capacities of from 4.7GB to 17GB and access rates of 600 KBps to 1.3 MBps. One of the best features of DVD drives is that they are backward-compatible with CD-ROMs. This means that DVD players can play old CD-ROMs, CD-I disks, and video CDs, as well as new DVD-ROMs. Newer DVD players, called second-generation or DVD-2 drives, can also read CD-R and CD-RW disks.

DVD uses MPEG-2 to compress video data.