Made for TV Movie
If it were any good, it would have been in theaters!—Martha, Martha Speaks
A one-off two-hour (usually) story, made to be shown on television as opposed to in cinemas. Also, a Miniseries can be comprised of 2 (or several) 2-hour long installments. They will be ~90 minutes on DVD because of the lack of commercial breaks.
Examples: National Lampoon's Thanksgiving Reunion, The Perfect Husband: The Laci Peterson Story.
The plots of made-for-TV movies are often Ripped from the Headlines. For example, the Amy Fisher affair of the early '90s spawned at least three made for TV movies. They are often full of Glurge and/or melodrama, and are often marked for their low quality (a stereotype that is exemplified by Syfy Original Movies, which are often watched solely for the Narm Charm). The exception to this rule seems to be HBO, whose own telefilms are usually quite well-made and have even won awards, thus "making up" for the lack of act breaks. Most made-for-TV movies are targeted at female audiences (e.g.: Hallmark films; Mother May I Sleep With Danger?, or any other Lifetime Movie of the Week), while the aforementioned Syfy and other movies are targeted at men.
Oftentimes, theatrically-released movies will get made-for-TV sequels, such as Revenge of the Nerds 3 and 4. Also, regular weekly series will sometimes get these as a variation of The Movie -- Doctor Who is perhaps the best-known example, the 1996 TV movie being its only episode in the extended hiatus between the 1989 and 2005 seasons.
A number of TV movies have been released theatrically overseas after airing in the United States, most notably Duel a 1971 suspense thriller starring Dennis Weaver directed by an up-and-coming young filmmaker named Steven Spielberg.
Western Animation have taken to doing this as of late due to CGI becoming the dominate animation in theaters, regulating most of 2-D films to TV. At a time during the 80s and 90s, having a theatrical film based on a TV cartoon was quite an honor (if not mostly for marketing purposes). But nowadays if a show is very successful, getting a TV movie would be the highest they could take the show (with a few exceptions if the network is feeling lucky such as The Simpsons Movie). Most animators would also use a TV movie as a Grand Finale as well.
One advantage of the form: situations can come to quite a head to build suspense to be retained over an Act Break. Another: there is usually no need to maintain a status quo; thus there is usually no Contractual Immortality. The possibility that Anyone Can Die (even the character the audience is rooting for) is far more likely, heightening dramatic tension. Then again, the latter can be said about cinema films. The downside, a reduced budget which can make production values look cheap. Special Effect Failure is much more likely here then on the big screen.
In the United Kingdom, this is not called a "TV movie", but rather a "one-off drama", and is generally seen as being more serious and artistic than a series, rather than the reverse.