When DVD technology first appeared in households, users were simply popping DVD discs into their DVD players to watch movies — an attractive option to the then-conventional VCR. But just as compact disc (CD) technology evolved so that users could record and erase and re-record data onto compact discs, the same is now true of DVDs. With so many different formats — DVD+R, DVD+RW, DVD-RAM, DVD-R, DVD-RW, DVD-ROM — how do users know which DVD format is compatible with their existing systems, and why are there so many different formats for DVDs? The following information sheds some light on DVD's different flavors, the differences between them and the incompatibility issues that the differing technologies have sprouted. The crucial difference among the standards is based on which standards each manufacturer adheres to. Similar to the old VHS/Beta tape wars when VCRs first hit the markets, different manufacturers support different standards. Additionally, the different variations on the term DVD (e.g. +R, -R, -ROM, and so on) describe the way data is stored on or written to the disc itself. These are called physical formats. DVD+R and DVD+RW DVD+R and DVD+RW formats are supported by Philips, Sony, Hewlett-Packard, Dell, Ricoh, Yamaha and others. DVD+R is a recordable DVD format similar to CD-R. A DVD+R can record data only once and then the data becomes permanent on the disc. The disc can not be recorded onto a second time. DVD+RW is a re-recordable format similar to CD-RW. The data on a DVD+RW disc can be erased and recorded over numerous times without damaging the medium. DVDs created by a +R/+RW device can be read by most commercial DVD-ROM players.

Key Terms To Understanding DVD Formats:   DVD Short for digital versatile disc or digital video disc, a type of optical disk technology similar to the CD-ROM. DVD-Video A video format for displaying full-length digital movies. DVD-ROM A type of read-only compact disc that can hold a minimum of 4.7GB (gigabytes), enough for a full-length movie. burn Slang term meaning to write data to a CD-ROM or DVD-ROM. Divx Short for Digital video express, a new DVD-ROM format promoted by several large Hollywood companies. With Divx, a movie (or other data) loaded onto a DVD-ROM is playable only during a specific time frame, typically two days.

DVD-R, DVD-RW and DVD-RAM
These formats are supported by Panasonic, Toshiba, Apple Computer, Hitachi, NEC, Pioneer, Samsung and Sharp. These formats are also supported by the DVD Forum.

DVD-R is a recordable DVD format similar to CD-R and DVD+R. A DVD-R can record data only once and then the data becomes permanent on the disc. The disc cannot be recorded onto a second time. There also are two additional standards for DVD-R disks: DVD-RG for general use, and DVD-RA for authoring, which is used for mastering DVD video or data and is not typically available to the general public.

DVD-RW is a re-recordable format similar to CD-RW or DVD+RW. The data on a DVD-RW disc can be erased and recorded over numerous times without damaging the medium.  DVDs created by a -R/-RW device can be read by most commercial DVD-ROM players.

DVD-RAM discs can be recorded and erased repeatedly but are compatible only with devices manufactured by the companies that support the DVD-RAM format. DVD-RAM discs are typically housed in cartridges.

DVD+R DL and DVD-R DL
Dual layer technology is supported by a range of manufacturers including Dell, HP, Verbatim, Philips, Sony, Yamaha and others. As the name suggests, dual layer technology provides two individual recordable layers on a single-sided DVD disc. Dual Layer is more commonly called Double Layer in the consumer market, and can be seen written as DVD+R DL or DVD-R DL.

DVD+R DL (also called DVD+R9) is a Dual Layer writeable DVD+R.
DVD-R DL (also called DVD-R9) is a Dual Layer writeable DVD-R. The dual layered discs can hold 7.95GB
The dual layered discs (DVD+R9 and DVD-R9) can hold 7.95GB and double sided dual layer (called dvd-18) can hold 15.9GB.

HD-DVD
Short for high definition-DVD, a generic term for the technology of recording high-definition video on a DVD. In general, HD-DVD is capable of storing between two and four times as much data as standard DVD. The two most prominent competing technologies are Blu-ray and AOD.

Blu-ray Disc (BD) - uses a 405nm-wavelength blue-violet laser technology, in contrast to the 650nm-wavelength red laser technology used in traditional DVD formats. The rewritable Blu-ray disc, with a data transfer rate of 36Mbps (1x speed) can hold up to 25GB of data on a single-layer disc and 50GB on a dual-layer disc. On a 50GB disc, this translates into 9 hours of high-definition (HD) video or approximately 23 hours of standard-definition (SD) video. The Blu-ray format was developed jointly by Sony, Samsung, Sharp, Thomson, Hitachi, Matsushita, Pioneer and Philips, Mistubishi and LG Electronics.

Advanced Optical Disc (AOD) - AOD and Blu-ray are similar in that they both use 405nm-wavelength blue-violet laser technology. while Blu-ray has a storage capacity of 25GB on a single-layer disc, AOD has a storage capacity of 20GB on a single-layer disc. and the capacity to hold 30GB on a dual-layer disc. AOD was developed jointly by Toshiba and NEC.

DVD-ROM
DVD-ROM was the first DVD standard to hit the market and is a read-only format. The video or game content is burned onto the DVD once and the DVD will run on any DVD-ROM-equipped device. DVD-ROMs are similar to CDs.

Non-standardized DVD formats
DVD-VCD is a DVD-Video disc that has data on it that has been encoded by using the MPEG-1 video format with the same definitions VCD has.

DVD-SVCD is also not a valid DVD standard, since the DVD standard does not support the SVCD resolution. The term DVD-SVCD is used to describe a hacked, or non-standard DVD-Video disc that has SVCD compatible content on it.

DVD-MP3 is created with and contains only digital audio files in the MP3 format. Not all DVD players can play DVD-MP3 discs.

A Note on DVD Burners
Until 2003 consumers would have to choose a preferred DVD format and purchase the DVD media that was compatible with the specific DVD burner. In 2003 Sony introduced a multi-format DVD burner (also called a combo drive or DVD-Multi) and today many manufacturers offer multi-format DVD burners which are compatible with multiple DVD formats.