Genre

A genre (from Latin: genus - race) is a category, in which you separate different media pro-ducts, which have special points in common. Examples for film genres are horror films, drama and thriller. This genres can also be separated into different sub-genres (political thriller, psycho thriller).

Movies of the same genre always have some things in common. So a thriller always has a hero, a bad guy and a mystery. The thriller genre is different from most other genres, because on the surface many of them look totally different from each other.

So are in the psycho-logical and supernatural thriller Red Lights, which is about the mystery of a magician and a scientist, who try to solve it and gets confronted with super-natural happenings, no guns, no big explosions and no police man.

 That stands in opposite to the action-thriller US Marshals, which involves a lot of shooting guns, explosions and policemen.

Nevertheless they have some basic things in common. We have a hero in both films, as well as a bad guy, as well as a mystery, which has to be solved and in both of the films we have a twist in the plot. The thriller genre uses suspense, tension and excitement as it main themes.   

Although a lot of thrillers are very different from each other, thrillers of the same sub-genre show a lot similarities. Often already the posters are quite similar.
This poster are from movies of the thriller  sub-genre crime(gangster)-thriller. 
All of them are quite dark and you can't see much. That symbolizes the mystery of crime and the secrets the men have. The guns or dead bodies are signifying violence, which also every of this movies has in common. 
Also the dark hues of the colors are quite similar.
The whole expression we get from this poster are mysterious and secretive and we know that this men are involved in mysterious and criminal things.

         

But there are much more thriller sub-genres than just the action, psycho-, supernatural and crime thrillers. There are political thriller like JFK or All The Presidents Men, which can be set against the backdrop of a political struggle, justice thriller like 12 Angry Men or Runaway Jury, which are about court cases.

I would like to make a crime thriller, with a psychopathic bad guy, who not only attacks the psyche of the main characters but also attacks the psyche of the audience and make them feel uncomfortable about themselves, because it always fascinated me, when the bad guy in the movie broke  every rule, even the rules of the bad guys, when he did the most horrible things, which disgust and shocked the audience up to their innermost, but always was liked by the audience. You could even laugh about him sometimes. But always a cold chill run trough your back, when this guy appears. Examples for this characters are: 'Hannibal Lecter'(Silent of the Lambs), 'The Joker' (The Dark Knight)and the contract killer in Road to Perdition.