Stands for "Digital Versatile Disc." A DVD is a type of optical media used for storing digital data. It is the same size as a CD but has a larger storage capacity. Some DVDs are formatted specifically for video playback, while others may contain different types of data, such as software programs and computer files.
The original "DVD-Video" format was standardized in 1995 by a consortium of electronics companies, including Sony, Panasonic, Toshiba, and Philips. It provided a number of improvements over analog VHS tapes, including higher quality video, widescreen aspect ratios, custom menus, and chapter markers, which allow you to jump to different sections within a video. DVDs can also be watched repeatedly without reducing the quality of the video and of course, they don't need to be rewound. A standard video DVD can store 4.7 GB of data, which is enough to hold over 2 hours of video in 720p resolution, using MPEG-2 compression.
DVDs are also used to distribute software programs. Since some applications and other software (such as clip art collections) are too large to fit on a single 700 MB CD, DVDs provide a way to distribute large programs on a single disc. Writable DVDs also provide a way to store a large number of files and back up data. The writable DVD formats include DVD-R, DVD+R, DVD-RW, DVD+RW, and DVD-RAM. While the different writable DVD formats caused a lot of confusion and incompatibility issues in the early 2000s, most DVD drives now support all formats besides DVD-RAM.
A standard DVD can hold 4.7 GB of data, but variations of the original DVD format have greater capacities. For example, a dual-layer DVD (which has two layers of data on a single side of the disc) can store 8.5 GB of data. A dual-sided DVD can store 9.4 GB of data (4.7 x 2). A dual-layer, dual-sided DVD can store 17.1 GB of data. The larger capacity formats are not supported by most standalone DVD players, but they can be used with many computer-based DVD drives.