From Wikipedia:
"Horror is a genre of speculative fiction which is intended to frighten, scare, or disgust. Literary historian J. A. Cuddon defined the horror story as "a piece of fiction in prose of variable length... which shocks, or even frightens the reader, or perhaps induces a feeling of repulsion or loathing". Horror intends to create an eerie and frightening atmosphere for the reader. Horror is often divided into the psychological horror and supernatural horror sub-genres. Often the central menace of a work of horror fiction can be interpreted as a metaphor for larger fears of a society. Prevalent elements include ghosts, demons, vampires, werewolves, ghouls, the Devil, witches, monsters, extraterrestrials, dystopian and post-apocalyptic worlds, serial killers, cannibalism, psychopaths, cults, dark magic, satanism, the macabre, gore and torture."