When you see the term "DVD", you mostly think of the DVD discs, such as movies and games. DVD is in reality several separate but codependent systems providing storage and DVD playback capability.
DVD Mastering
Any time that a movie, game, or other group of media has been created and it is decided that the storage and playback format will be DVD, the mastering process formats this data so that it can be read and decoded by DVD players.
Before formatting is complete to disc, digital video contains an extremely large amount of stored information. Using the MPEG-2 digital video encoding standard, digital mastering can take this information and change it to a format much more manageable by the common DVD player. By eliminating redundancies (elements that are almost identical), encoding eliminates over 97 percent of the data without noticeably affecting image quality.
Digital Video Discs
A digital video disc is made up of a reflective aluminum foil encased in a clear plastic. Data is stored on the foil as a series of tiny pits formed in a tight spiral on the disc. The pits are formed in the foil by stamping it with a glass master. For a double-sided disc, two halves, each with their foil full of data, are bonded back to back.
DVD Players
DVD players consist of a disc reader, signal processor, decoder, and a microcontroller. Each part of the player controls one phase of the decoding and displaying process.
The reader is the physical motor which spins the disc and the laser which reads the information from it. Unlike audio CDs, DVD readers use red light.
The digital signal processor is an integrated circuit that translates the laser pulses back into electrical form that other parts of the decoder can use. The digital audio/video decoder reconstitutes the compressed data on the disc, converting it into output for computers, TV monitors, and stereo systems.
The microcontroller translates remote control, front panel, or other software input into commands for the audio/video decoder and the disc reader mechanism. The microcontroller is responsible for implementing parental lockout, dialing distributors for access codes and controlling decryption.
There is a difference between DVD-Video and DVD-ROM. DVD-Video (often simply called DVD) holds video programs and is played in a DVD player hooked up to a TV. DVD-ROM holds computer data and is read by a DVD-ROM drive hooked up to a computer. The difference is similar to that between Audio CD and CD-ROM. DVD-ROM also includes recordable variations (DVD-R, DVD-RAM, DVD-RW;3). New computers with DVD-ROM drives can also play DVD-Videos