Video on demand (VOD) is a programming system which allows users to select and watch/listen to video or audio content such as movies and TV shows whenever they choose, rather than at a scheduled broadcast time, the method that prevailed with over-the-air programming during the 20th century. IPTV technology is commonly used to bring VOD to televisions and personal computers.Television VOD systems can stream content through either a set-top box, a computer or other device, allowing viewing in real time, or download it to a device such as a computer, digital video recorder (also called a personal video recorder) or portable media player for viewing at any time. The majority of cable- and telephone company–based television providers offer:

VOD streaming, whereby a user selects a video program and it begins to play immediately on the television set, or
downloading to a digital video recorder (DVR) rented or purchased from the provider, or downloading onto a PC or to a portable device, for viewing in the future.Internet television, using the Internet, is an increasingly popular form of video on demand. VOD can also be accessed via desktop client applications such as the Apple iTunes online content store.
Some airlines offer VOD as in-flight entertainment to passengers through individually controlled video screens embedded in seatback or armrests or offered via portable media players. Some video on demand services, such as Netflix, use a subscription model that requires users to pay a monthly fee to access a bundled set of content, which is mainly movies and TV shows. Other services use an advertising-based model, where access is free.