Video on demand (VOD) is a system which allow users to select and watch/listen to video content on demand. IPTV technology is often used to bring video on demand to televisions, connected devices and personal computers. Catch up TV is a form of video on demand as services like iTunes and Google Play.
Often quoted also as TVOD (Transactional Video on Deman), it usually requires the users to commit to a specific payment for each content they wish to watch.
VOD services can be funded also by advertising (AVOD) or by subscriptions (SVOD).