A film that is released direct-to-video (also straight-to-video) is one which has been released to the public on home video formats first rather than first being released in movie theaters.
This can occur for several reasons. Often a production studio will develop a TV show or film which is not generally released due to poor quality, lack of support from a TV network, controversial nature, or simple lack of general public interest. Sometimes a film may be in post-production before the studio realizes how bad it is. Only able to grant a cinematic release to a limited number of films in a year, they may choose to pull the completed film from the theatres, but aim to recoup some of their losses through video sales and rentals.
The term is at times used as a derogatory term for sequels of films that are not expected to have financial success.
Direct-to-video releases are generally considered to be of lower technical or artistic quality than theatrical releases. Some studio films that are released direct-to-video are films which have languished for some time without release, either because the studio doubts its commercial prospects would justify a full cinema release or because its "release window" has closed — that is, it may have been rushed into production to capitalize on a timely trend or personality and not been completed in time. In film industry slang, such films are referred to as having been "vaulted."
Direct-to-video releases are also done for films which sometimes cannot be shown theatrically, because of their content (they may be too controversial for theaters) or because the cost involved in a theatrical release is prohibitive to the releasing company. Almost all pornographic films are released direct-to-video.
Animated sequels and movie-length episodes of animated series are also often released this way; The Walt Disney Company in the 1990s began making sequels of most of its animated films for video release.
The Direct-to-DVD market
The popularity of DVDs has made the term Direct-to-DVD widely replace "Direct-to-video". However, the lucrative market for DVDs has taken away some of the stigma of a straight-to-DVD release. Some minor films can be made with a small budget and turn a profit on DVD sales alone, and some are made specifically for this purpose.
The V-cinema and OVA markets in Japan
Japan has a different weight to the Direct-to-video movement. Rather than being renowned for poor storylines and effects (though they are low-budget), so-called V-cinema has more respect from the public, and affection from film directors for the greater creative freedoms allowed by the medium.
For anime, this is called Original Video Animation (OVA or OAV), and their production values usually fall between television series and movies. As such, they somewhat lack the stigma of poor quality. They are often used to tell stories too short to fill a full tv season, particularly in the early 1990s. With the advent of the 13 episode season format, OAVs are less common now. Some are used to garner enough interest in fandom to make a profitable full television series.