What defines Film Noir

From the excerpt "A Bright and Guilty Place," I gather film noir focuses primarily on crime and passion.  Literally speaking, film noir translates to "black film," which, taking an educated guess, leads me to believe majority of these films are in black and white. Black and white films set the tone for an eery and suspenseful sort of plot, which I suspect are key ingredient in film noir.  Knowing very little thus far, when I imagine what film noir might focus on, The Great Gatsby by F. Scott Fitzgerald comes to mind.  Though this may be off entirely, being as how this story is set shortly after World War I, roughly 1922, I can see the relevance in the characteristics of Nick Carraway being that he is honest, and often a confidant for those in trouble, and Jay Gatsby, the protagonist of the story, who is willing to do whatever it takes, even murder, to achieve his ultimate goals: wealth and love.  Nick would be the "detective" so to speak, seeking truth and rescuing Daisy Buchanan, who has Gatsby's affection, whereas Gatsby would be the shady character who is suspicious and underhanded, overtaken by his need for power, wealth, admiration, and love from Daisy.  Film noir seems to have similar characters and story lines: a leading man of integrity, a villain who is usually obsessed with greed, lust, power, or something of the like, and leading lady who is somehow conflicted between the two.  As pieces fall together and new information comes to light, the climax of the story comes to a resolve as the entwined characters unravel the mystery and tragedies to ultimately reveal the truth.