From Wikipedia: http://en.wikipedia.org/wiki/Video_on_demand
Video on demand (VOD) systems allow users to select and watch video and clip content over a network as part of an interactive television system. VOD systems either “stream” content, allowing viewing in real time, or “download” it in which the program is brought in its entirety to a set-top box before viewing starts. The latter is more appropriately termed “store and forward“. The majority of cable and telco based VOD systems use the streaming approach, whereby a user buys or selects a movie or television program and it begins to play on the television set almost instantaneously.
