Genre is a style or category of art, music, or literature. Genre controls what authors write and how it is written. It describes the style and focus of the novel as well as character types, settings, themes, and plots. For instance, certain settings suit specific genres. These vary in type, details, intensity, and length of description.
There are often sub-genres within genres, for example, a fantasy story with sinister, frightening elements would belong to the dark fantasy sub-genre or even horror.