Video on Demand (VOD) or Audio Video on Demand (AVOD) are systems which allow users to select and watch/listen to video or audio content on demand.
Television VOD systems either stream content through a set-top box, 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 telco-based television providers offer both VOD streaming, such as pay-per-view, whereby a user buys or selects a movie or television program and it begins to play on the television set almost instantaneously, or downloading to a DVR rented from the provider, for viewing in the future. Internet television, using the Internet, is an increasingly popular form of video on demand.
Some airlines offer AVOD as in-flight entertainment to passengers through individually-controlled video screens embedded in seatbacks or armrests or offered via portable media players. Airline AVOD systems offer passengers the opportunity to select specific stored video or audio content and play it on demand including pause, fast forward, and rewind.