Film Noir (literally 'black film or cinema') was coined by French film critics (first by Nino Frank in 1946) who noticed the trend of how 'dark', downbeat and black the looks and themes were of many American crime and detective films released in France to theatres following the war
Film Noir is the flip side of the all-American success story. It's about people who realize that following the program will never get them what they crave. So they cross the line, commit a crime and reap the consequences. Or, they're tales about seemingly innocent people tortured by paranoia and ass-kicked by Fate. Either way, they depict a world that's merciless and unforgiving.
Film Noir is a sub-genre of crime films that developed in the United States during World War II that featured people acting out of desparation in a bleak and morally ambiguous world. They were made in black and white, and had a dark, high-contrast, expressionistic visual style. Film Noir is primarily based on the hard-boiled crime fiction of the thirties (many Films Noir were adaptations of those novels) and the dark gangster films of the thirties.