What Is DVD?

DVD (Digital Versatile Disc or Digital Video Disc) is the next generation of optical disc storage media format. A DVD has the same physical dimensions as a normal CD. But a DVD can store more than 6 times of data comparing to a normal CD.
DVDs are produced in two physical sizes: 120 mm, 12 cm or 4.72 inches and 80 mm, 8cm or 3.15 inches.
Digital data may be recorded on a DVD in 4 different ways resulting different capacities:
DVD-5: Single sided and single layer (SL) on a 12 cm disc stores 4.7 GB of data.
DVD-9: Single sided and dual layer (DL) on a 12 cm disc stores 8.5 GB of data.
DVD-10: double sided and single layer (SL) on a 12 cm disc stores 9.4 GB of data.
DVD-18: double sided and dual layer (DL) on a 12 cm disc stores 17.1 GB of data.
DVD can be used to store data, audio, or video data with different file directory structures. But they all share the same common formatting characteristics:

A single track of raw data with block size of 2048 bytes.
An ISO file system is located at the beginning of the track.
One popular type of DVD is called DVD-Video, which is to store high quality video data, movies. See next section for details.
Another type of DVD is called DVD-Audio, which is to store high quality audio data, music and songs.