The phrase crime noir means a lot of different things, primarily because people have different ideas about what the term means. Noir is the French word for dark and crime noir films are indeed dark stories.
As time has passed the genre has both expanded and been sub-divided. You can enjoy stories called hardboiled noir, tech noir, neo noir, and crime noir.
What makes a novel, a film, or a story of any kind a noir? That can be a difficult question to answer with any degree of clarity. So I’ll let people who have invested a lot of time and effort in answering that question do so in the form of links to Youtube videos I have found on the subject.
It’s fascinating and like most things, the more you know about crime noir and all its tropes, quirks, and details, the more you can enjoy the genre and all of its sub-divisions.
Detective Fiction: Dashiell Hammett or Raymond Chandler
Los Angeles: City of Film Noir
The Art of Shadows: A Short Film Noir Documentary
The Basics of Lighting for Film Noir
Bladerunner: Constructing a Future Noir
