Thriller as a Genre

Thriller as a genre is what adds to make a thriller for example: types of characters , locations, what is the aim is it continuous, 

Characters that often occur in thrillers:

Convicts, criminals, stalkers, assassins, down-on-their-luck losers, innocent victims (often on the run), prison inmates, menaced women, characters with dark pasts, psychotic individuals, terrorists, cops and escaped cons, fugitives, private eyes, drifters, duplicitous individuals, people involved in twisted relationships, world-weary men and women, psycho-fiends, and more

The themes of thrillers frequently include terrorism, political conspiracy, pursuit, or romantic triangles leading to murder.

'Thriller and Suspense Films are types of films known to promote intense excitement, suspense, a high level of anticipation, ultra-heightened expectation, uncertainty, anxiety, and nerve-wracking tension. Thriller and suspense films are virtually synonymous and interchangeable categorizations, with similar characteristics and features.'

http://www.filmsite.org./thrillerfilms.html

Alfred Hitch-cock  was a very iconic and legendary filmmaker and director he first directed in 1925 and when he rose to become famous his films were well known as full of suspense and psychological aspects were always used this picture above is from a Hitch cock film called rear window which is also the fifth most popular thriller film according to IMDB votes.