There are several different types of OTT videos
SVOD Subscription Video On Demand. This is the type most commonly associated with OTT. Users pay a monthly or yearly subscription to watch content. Examples include Netflix and Disney Plus.
AVOD Advertising Video On Demand. Here the content is delivered either free or at a lower price alongside advertising. Examples include Pluto TV and Peacock.
TVOD Transactional Video On Demand. Essentially pay-per-view. This is primarily used for movies or for streaming live sporting events.
FAST Free Advertising Supported Television. Advertising-driven, scheduled linear TV channels created from existing on-demand content catalogs.
Note. Many providers are starting to offer tiered services that offer different types of OTT services at different price points i.e. a premium SVOD service with a cheaper AVOD service alongside it.