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. Some made-for-TV movies are targeted at female audiences (e.g.: Hallmark Hall of Fame films; Mother May I Sleep With Danger?, or any other Lifetime Movie of the Week), while the aforementioned Syfy movies and other films are targeted at men.
It wasn't always like this. In the 1970s, American television networks began producing 90- to 120-minute TV movies as a new form of serialized television, and despite the low budgets and quick shooting schedules, managed to attract a lot of name talent whose schedules otherwise prevented them from committing to a television series. Many of them got big ratings; it was often that you could see a TV movie pull in one-third and even half of the television-watching public. However, increasing budgets and the rise of cable television led to a decline of quality to the point where the glory days were forgotten and replaced by low budgets, Strictly Formula plots, and bad acting. Nowadays, the Big Four prefer to be more conservative with budgets while TV movies are strictly done for cable and/or streaming, where many networks have more money to spend due to being light on in-house production. Also helping is that with many cable networks and streaming services getting into the series business, actors who in the past had to be content with taking a TV movie role in between jobs can happily reject them for a much more lucrative and satisfying role in a show guaranteed to make 10 episodes at the least rather than being reduced to paint-by-numbers Damsel in Distress fare; those that want to stick with TV movie-like roles can instead take work in much shorter true crime reenactment shows airing on Lifetime, Investigation Discovery, A&E and the network newsmagazines.
Sometimes, 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.
Several science fiction series (particularly those with a more narrow fanbase, in which case the economic return for such a movie will be lower) have released these as well, often as a Reunion Show or Wrap It Up. The Pretender used a couple of them to tie up the loose ends of its Myth Arc, as did Stargate SG-1. Despite the lower budget, they can still be worth watching; Stargate: Continuum was particularly good, as were Star Trek: Voyager's telemovies in its later years.
A number of TV movies have been released theatrically overseas after airing in the United States. This was especially common in the 1970s to ensure that the studios made quicker profits on these movies. One such example is Duel, a 1971 suspense thriller starring Dennis Weaver directed by an up-and-coming young filmmaker named Steven Spielberg. A peculiar recent example is the Liberace Biopic Behind the Candelabra, which was reportedly rejected by US film studios for its gay subject matter, was made as a TV movie by HBO, and then did get a cinematic release in many overseas markets.
Then there's the situation where the television movie effectively serves as The Movie for a TV series. This has been especially common in Western Animation since the mid-2000s, as a result of both CGI becoming the dominant form of animation in theaters and the huge influx of mixed quality television-to-film adaptations in the early 2000s causing the movie-going public to view all such efforts as going outside to pay for something that they've been getting at home for free for the past five years. Nowadays, if a show is very successful, getting a TV movie is the furthest that the property will be taken unless the studio is feeling lucky or the series has greatly ingrained itself into pop culture, such as with The Simpsons Movie. In any case, if your favourite television characters end up starring in a 90-minute adventure, expect it to be a Big Damn Movie that also doubles as the Grand Finale.
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 is a reduced budget, which can make production values look cheap. Special Effect Failure is much more likely here than 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, not unlike how OVAs are viewed relative to anime made for broadcast television. Until the late '80s/early '90s they were called "plays" and were often videotaped on multi-camera, which gave them a more theatrical look; occasionally they were even direct adaptations of works written for the stage. Sometimes they'd even end up spawning an ongoing TV series; Rumpole of the Bailey and The Bill can trace their origins back to one-off dramas included in The BBC's Play For Today and ITV's ITV Playhouse anthology strands respectively.