[Penforhire]

Reasonable question.

Urban means, to me, placed in the 1900's or later and in cosmopolitan settings that a traveller would recognize, at least in tone if not in specifics (fictional cities work). It seems most common to overlay the plot onto actual, real, regions.

I know that isn't the "correct" definition, which allows much earlier settings. To me those move the genre toward other labels like historical or Roman.

Dark means, to me, a tendency toward seriousness, despair, or drama with less comic relief and more examination of what we think of as sinful or unethical behavior. To use a punch line, "less Disney, more real life." It doesn't have to strictly be horror but it tends to be a struggle with something horrible, evil, immoral, or seamy. The good guys can still triumph without defining it as Disney but they should get some dirt on them.

In combination with fantasy, it doesn't have to involve demons or any other sort of mythical creature. It could be, for example, a psychic person, from serial killer to abused child.