What is a DVD?
DVD was originally said to stand for Digital Video Disc or Digital Versatile Disc. A DVD player or a computer equipped with a DVD drive is required to play DVDs. Almost all DVD players also play VCDs.

What are those in a DVD?
There is a folder named "VIDEO_TS" in a DVD. There are three types of file within the "VIDEO_TS" folder: IFO, VOB and BUP.
The IFO file, which refers to "information", is a file with the navigation information for the DVD. Generally an IFO file contains the information for a title in the DVD.
The VOB file, which refers to "video object ", is a file with video and audio data for the related content of the DVD. Generally, there are a few VOB files for an IFO file to control.
The BUP file, which refers to "backup", is an exact copy file of IFO file. It will be used if the DVD can't read an IFO file in case that there is a scratch on the disc or other error.

Other information about Blu-ray or DVD

DVD Video
For viewing movies and other visual entertainment, the total capacity is 17 gigabytes if two layers on both sides of the disk are utilized.

DVD-ROM
Its basic technology is the same as DVD Video, but it also includes computer-friendly file formats. It is used to store data.

DVD-R
Its capacity is 4.7 gigabytes. Originally designed for professional authoring, a version for general consumer use is now under development. As with CD-R, users can write only once to this disk.

DVD-RAM
TThis makes DVD a virtual hard disk, with a random read-write access. Originally a 2.6-GB drive, its capacity has increased to 4.7-GB-per-side. It can be re-written more than 100,000 times.

DVD-RW
Similar to DVD-RAM except that its technology features a sequential read-write access more like a phonograph than a hard disk. Its read-write capacity is 4.7 gigabytes per side. It can be re-written up to about 1,000 times.

DVD Audio
The latest audio format more than doubles the fidelity of a standard CD. It is expected to become the most popular audio disk.

Blu-ray Disc
Blu-ray Disc (official abbreviation BD) is an optical disc storage medium designed to supersede the DVD format. The standard physical medium is a 12 cm plastic optical disc, the same size as DVDs and CDs. Blu-Ray Discs contain 25 GB per layer, with dual layer discs (50 GB) the norm for feature-length video discs and additional layers possible in the future.