Film noir is a term used to describe crime drama movies from Hollywood that are often focused on sex, crime, and corruption. 

Film noir movies were mostly made from the early 1940s to the late 1950s in the United States, and they were usually filmed in black-and-white. The term "film noir" comes from the French term for "black film" or "dark film". Film noir movies include many different genres of movies, such as gangster movies, police movies, and detective movies. 

Film noir movies were often filmed so that there were many dark shadows in the movie, even on characters' faces. The Hollywood film noir movies were influenced by German film directors such as Fritz Lang, who used dramatic lighting techniques. Another influence on film noir movies was 1930s French books or movies about heroes who would die at the end of the story or stories with sad endings. Film noir movies were also influenced by crime fiction, such as the detective and crime stories by Dashiell Hammett, James M. Cain, and Raymond Chandler.

Examples of film noir movies and actors 
Some important film noir movies are: Stranger on the Third Floor (1940); The Maltese Falcon (1941) Double Indemnity (1944) The Big Sleep (1946) The Postman Always Rings Twice (1946); Key Largo (1948);Kiss Me Deadly (1955), and Touch of Evil (1958). 

The important actors from Hollywood film noir movies were Robert Mitchum, Humphrey Bogart, and Peter Lorre.

Movies from after the film noir period 
The film noir period was the 1940s and 1950s. Even in the years after the 1950s, some movies were made in the film noir style. In the 1960s and 1970s, there were movies like The Manchurian Candidate (1962) and Chinatown (1974), which were influenced by the film noir movies from the 1950s.

In the 1980s and 1990s there were movies that were a bit like film noir movies, like Body Heat (1981), Basic Instinct (1992), Kill Me Again (1989), Red Rock West (1992), and Fargo (1996). In the 2000s, there are also movies that are like film noir movies in some ways. For example, there are films such as Memento (2000) and Sin City (2005). 

There are also science fiction movies that look a bit like film noir movies because they look dark and they have a lead character who does some bad things, such as Soylent Green (1973); Blade Runner (1982), which starred Harrison Ford; and Minority Report (2002), which starred Tom Cruise.

Things seen in film noir movies 
Film noir movies are often shot in cities at night, and the stories often take place in bars, nightclubs, gambling clubs, casinos, and cheap hotels. This makes film noir movies look very dark, because the scenes are shot at night, or inside dark places like a bar or hotel.

Film noir movie scenes often have a lot of shadows, such as the shadows of window frames, blinds, or stair banisters. There are also often dark shadows on the movie scenes, even on the faces of the actors. All of the shadows and darkness make the film noir movies feel mysterious and stressful. 

The characters in film noir movies are often motivated by greed, jealousy, or revenge. The characters in film noir movies are often private detectives or police officers who are investigating crimes committed by bad criminals and gang members such as murder, gambling or prostitution. In film noir movies, there are often stories about robberies, heists, extortion of money (which is called "blackmail"), or murder.

Watching film noir movies 
In film noir movies, even the heroes or lead characters are often bad or partly bad in some way. For example, the hero of a film noir movie may help an innocent man or woman who is being threatened by a criminal, or rescue a woman from a criminal gang. Yet the hero or lead character may also do bad things, such as commit crimes, hurt or threaten people, or tell lies. 

Often, the hero or lead character of a film noir film will be bitter, sad, lonely, or depressed, because of bad things that happened to them. The person watching the movie has to decide if they think that a hero who does both good and bad things is a good person or not. The stories from film noir movies can make the audience think about how people should act, or how people should make choices in their life. This is one of the things that people like about watching film noir movies.

Film noir movies are not happy movies. In happy movies, like romance movies, people fall in love, get married, and live happy lives. In film noir movies, sad things happen. A good man with a wife might need money for their rent, and borrow the money from a criminal gang leader, because the good man has no other way of getting the money. Then the bad gang leader might force the good man to do bad things to pay back the money. Maybe the bad gang leader will threaten to hurt the good man's wife. Then the good man has to decide between protecting his wife or doing a bad crime. 

People who watch film noir movies like to see stories about people who have to make hard choices, or people whose lives have sad things happen in them. Real life is not a romantic comedy; people often have to make hard choices or have sad things happen.

Books about film noir 
Robert Ottoson wrote a book in 1981 about film noir called A Reference Guide to the American Film Noir: 1940–1958.

Other websites 
 "A Guide to Film Noir Genre" by Roger Ebert 
 Aesthetics of film noir