A genre is a category of media products that are identified as being a similar form/type such as action, adventure,drama, romance, comedy (black), suspense, and even epics and westerns, and they often take a denunciatory approach toward warfare. For example: Grease and Hairspray may come from different generations but they are both identified as musicals because musicals include key qualities such as singing throughout and performing. These two musicals both include the same key qualities so they are identified to the world as the same genre which is musicals.
Sub-genres in Thriller movies:
The thriller genre can include the following sub-genres, which may include elements of other genres

Action thriller: In which the work often features a race against the clock, contains lots of violence, and an obvious antagonist.
Conspiracy thriller: In which the hero/heroine confronts a large, powerful group of enemies whose true extent only he/she recognizes.
Crime thriller: This particular genre is a hybrid type of both crime films and thrillers that offers a suspenseful account of a successful or failed crime or crimes.
Disaster thriller: In which the main conflict is due to some sort of natural or artificial disaster, such as floods, earthquakes, hurricanes, volcanoes, etc., or nuclear disasters as an artificial disaster.
Drama thriller: In which the story consists of the elements of a thriller and drama film. These films are usually slower paced and involves a great deal of character development along with plot twists.
Erotic thriller: In which it consists of erotica and thriller.
Legal thriller: In which the lawyer-heroes/heroines confront enemies outside, as well as inside, the courtroom and are in danger of losing not only their cases but their lives.
Medical thriller: In which the hero/heroine are medical doctors/personnel working to solve an expanding medical problem.
Political thriller: In which the hero/heroine must ensure the stability of the government that employs him.
Psychological thriller: In which (until the often violent resolution) the conflict between the main characters is mental and emotional, rather than physical.
Spy thriller (also a subgenre of spy fiction): In which the hero is generally a government agent who must take violent action against agents of a rival government or (in recent years) terrorists.
Techno-thriller: In which (typically military) technology is described in detail and made essential to the reader's/viewer's understanding of the plot.
Religious thriller: In which the plot is closely connected to religious objects, institutions and questions.