be a bit about film noir? What is the meaning of quot;film noirquot; and what are its story conventions? Moreover, how and why did film noir emerge?...

Can you describe a bit about film noir? What is the meaning of "film noir" and what are its story conventions? Moreover, how and why did film noir emerge? In terms of film history, what was going on in cinema production and what kind of environment/atmosphere had been created by the studios? Finally, what are the themes and/or ideas to come out of film noir movies? That is, what kind of concepts, beliefs, ideologies are expressed within film noir? How/why is this the case?