Horror fiction is a category of writing in which a story is crafted to scare or otherwise horrify the reader. The story almost always follows some sort of narrative arch with an exposition, rising action, climax, resolution, and denouement, though this plot structure can be modified. The narration can be done from any point of view, though first and third person narrations are most common.
Supernatural horror fiction is one of the most common types of horror stories. These stories tend to focus on beings or situations that exist beyond the realm of humanity. Ghosts and monsters fall into this category, and the horror fiction in this case is often frightening because the protagonist does not have the knowledge necessary to defeat or otherwise avoid the supernatural being. The supernatural being is often far more powerful than humans, though the being very often has some sort of weakness that will ultimately lead to its downfall. Vampire stories, for example, focus on beings that are superior in strength and intellect in many cases, yet they are weakened or defeated in sunlight.
Psychological horror fiction presents a situation that affects the protagonist's ability to think clearly. The events that take place throughout the story are often not possible in reality, yet the character experiences them and therefore often doubts his or her sanity. Psychological fiction focuses primarily on the function of the human mind and the situations or events that can alter the mind's ability to function properly.
Sometimes horror fiction will focus on people or events that could feasibly take place in reality. The story then tends to be fairly gruesome, sometimes involving murder, mutilation, ritual sacrifice, or other horrific situations that can harm or kill a human being. Stories such as these often focus on unstable antagonists who have a penchant for murder or torture.
Traditional folklore often focused on the horrific or supernatural, so some readers might argue that horror stories have their origins in traditional texts or word of mouth stories. Many cultures often passed on stories of supernatural beings, strange disappearances, warnings to people behaving immorally, and stories of the nature of the afterlife. All horror fiction focuses on the emotions and thoughts that make people scared or uncomfortable, and in many cases, the stories revolve around hopelessness and bleakness from which the protagonist cannot escape.