A DVD (Digital Versatile Disc / Digital Video Disc) is an optical disc storage medium used to store and distribute digital data, including video, audio, software, and general files. It is read by a 650-nanometre red laser in a DVD drive, which detects microscopic pits and lands arranged along a continuous spiral track on one or more reflective layers inside the disc. Compared to a Compact Disc (CD), a DVD uses smaller pits, tighter track spacing, and more advanced error-correction, allowing much higher data density and capacity.
A standard single-layer DVD holds 4.7 GB of data, while dual-layer DVDs can store up to 8.5 GB by using two semi-reflective data layers that the laser can refocus between during reading. DVDs exist in several formats, including DVD-ROM (read-only, used for commercial movies and software), DVD-R / DVD+R (recordable, write-once), and DVD-RW / DVD+RW (rewritable).
DVDs were widely used for movie distribution (DVD-Video), software installation, data backup, and media playback on computers and standalone DVD players. Although largely superseded by Blu-ray discs, USB flash storage, and online streaming, DVDs remain relevant for legacy systems, physical media distribution, and offline access.