Horror takes our real life anxieties and fears and uses it to their advantage on screen to bring out the audience's fears. It takes inspirations from real world events occuring during the time period such as for example Frankenstein(1931), where the villagers trying to burn the creature represent american society during the Great Depression. Another example being Godzilla(1954), recreating the experiences of World War 2 and the atomic age. Such events influenced directors to bring back the emotion through their horror films. The genre was also used to communicate messages to society, such as towards teenagers on drugs, sexual activities to not fall prey to these potentially damaging activities. Movies communicating such ideas, Black Christmas(1974), Jaws(1975), A Nightmare on Elm Street(1984). 

To bring out the audience's fears and anxieties, horror uses a lot of blood and gore to give a sense of intense pain and disgust, sharp weapons such as knives to indicate danger and further fear. Unique camerawork and lighting was also utilized to make the monsters have a silhouette making them unknown to the audience to give them a eerie feeling of the unknown. 

Horror encompasses over 100 sub-genres and each horror film can be of any of those variants such as psychological, slasher, supernatural, or even comedy horror depending on the emotions and perceptions that the director intends the audience to experience. A reason why horror has so many subgenres is because it should be treated less as a genre but more as emotions of intensity, fear, shock or disgust which can be brought to the audience in various ways. 

Since the creation of horror films, it has been used as a reflection of the fears of our society and culture. Spanning such a large size with many variations. Early 1900s, the main medium used to bring out fears were ghosts, skeletons and the devil using supernatural and religious imagery. Films during this time period were focused on giving the audience a sense of amuse and humour instead of fear, which would follow along in the coming decade. Later in the 20th century horror films shifted from humor to more serious films. Also during this time, horror films were booming in Western Europe where the events of World War 1 and the troubling post war government rule were the influences in their films.

In early horror films, use of trick photography, double exposure, and practical effects to bring fictional characters to life. Films by Walter R. Booth used trick photography to create floating heads.

As mentioned in the first source, horror covers a vast number of subgenres. Early horror films were more humorous, taking the monsters and evil less seriously, while later films turned to the more serious side emphasizing on the fears and dangers influenced by real world events to further connect and impact the audience. Another subgenre that developed being psychological horror, using intense visuals, sound and expressions to increase the intensity faced on to the audience.

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Summary: 
1. Shadows: It is not surprising that one of the most popular strategies employed by horror filmmakers is the use of shadows since they appeal to a basic dread of the unknown and what might be hiding in the shadows. Almost always, the thought of what might be lurking in the shadows is more terrifying than what is actually there. In order to keep their audiences on edge, many horror filmmakers will experiment with this tactic during the course of their picture. In order to light the background rather than the subject and make the threatening element feel as though it doesn't belong in the scene, it is very common to photograph the major antagonist as a silhouette.

2. Uncommon Angles: In general, when working in the horror genre, directors have a lot of creative licence, and this definitely holds true when using uncommon camera angles. A typical approach for creating anxiety in your audience while they watch a drama is the off-kilter Dutch angle shot. This perspective provides the impression that the character is looking at the world upside down. Another unusual perspective that gives viewers the impression that the main protagonists are being observed by an unknown force is the birds eye view. Another common option for horror directors is POV shots. They frequently depict the restless energy of the victim or the antagonist in a drama.

3. Uncommon Lighting: One of the few genres, horror, doesn't light actors to make them look as attractive as possible. Instead, horror filmmakers frequently decide to use considerably more elaborate lighting schemes to illuminate their subjects. Popular methods include lighting from below, using only one flashlight beam, or using flickering lights.

4. When it comes to colour, horror film directors also have a lot of creative licence. It's not uncommon to see red or green splashes of colour in a horror movie because, similar to unique lighting techniques, horror writers and directors aren't frequently concerned with making their characters attractive. The audience might be made to feel scared and in danger by using excessive colours.

Link: https://musicbed.com/blog/career/creativity-filmmaking-david-f-sandberg

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