DVDs (Digital Video Disk) look like a CD but natively play an MPEG-2 compressed video file with AC-3 or some other audio file. DVDs come in DVD+R and DVD-R (also called a DVD5), Dual Layer (DVD9), and lately Blu-Ray and HD-DVD.

A DVD5 holds 4.7gigs of data, which, depending on the compression of the video file ranges from 1-4 hours. A DVD9 (or Dual Layer DVD) holds 8.5gigs. The DVD10 format seems to be passing away (a Dual Layer DVD where one side of the DVD is one layer and the other side holds the other).

Up and coming are Blu-Ray and HD-DVDs. These hold 30-60gigs of data and provide for a larger "throughput" for High Definition video. However, these are still very rare.

A Dual Layer DVD is Mastered by combining the two layers (Layer0 and Layer1) on a Glass Master.