Horror as a genre often consists of disturbing imagery or ideas. This is a widely enjoyed genre of media with many books, cinematic works, art pieces, songs, and games being birthed from the idea of disturbing the audience in an enjoyable manner.
The Oxford English Dictionary provides a multitude of definitions for the word horror
but the following are the most applicable for the horror movie topic:
a shuddering with terror and repugnance; strong aversion accompanied by dread; the feeling created and amplified by something shocking or frightful.
The second of which is the most commonly used and implied definition of horror
when it comes to the average horror movie.
Part of what makes horror such an attractive media is how it triggers intense emotions; in a world where so much is regulated and controlled, it gives the viewer adrenaline and excitement, something that is out of the ordinary for most people. Another reason is that the human body longs for emotion, but survival instincts prevent major and life-threatening risks. Horror, cinema and games especially, allow the audience to experience the adrenaline rush of fear while remaining in control. If a movie or game gets too scary, it can be turned off, but fear is still experienced.