Genres. What are they and why should I care about them?
Genres are the most common ways to sort stories into groups that contain like elements. Some genres have very specific reader expectations and others are more fluid. As a writer, tapping into a genre's tropes is critical to your success. This applies whether you want to feed the reader exactly what they expect,or if you want to shock and delight them with your own twists and turns.
Tropes give you a starting place in a general. Several genres are defined by those tropes. A Cozy Mystery, for example, is always a non-professional slueth stubbling upon something in real life and solving it using her skillset. They aren't violent and are usually quick, light reads where the author lays out clues and the reader figures things out along with the character in a story. If you describe a violent murder in what looks like a Cozy, most of your readers exit post haste.
A genre is usually one of the first filters applied by a reader. If you like to read Werewolf stories, there is a werewolf on the cover, but the opening scene is in a space battle with lasers blasting all over the place while in orbit of a desert planet, then you completely didn't align your genre. The reader was expecting a paranormal experience and you gave them Space Opera or Military Sci Fi. Sure, you can get get werewolves in space... but it so seriously subverts readers expectations that you'll end up with only the readers with the Venn diagram alignment of of "likes sci-fi" and "likes paranormal". This is a sharply lower potential audience pool than "Sci-Fi" or "Paranormal". There will be some diehard fans of your Werewolves in Space Epic, especially if you can pull off the writing, but you are walking the high wire without a net.Quote
Trope - a convention or device that establishes a predictable or stereotypical representation of a character, setting, or scenario in a creative work