The document discusses the history and definition of film genres, particularly the thriller genre. It notes that genres first emerged in the late 19th century with early films featuring swashbuckling adventure or romance narratives. The 1920s-1930s saw the rise of the thriller genre due to films by Alfred Hitchcock. Key characteristics that define genres include narrative conventions, character representations, and construction techniques like camerawork and music. Sub-genres are hybrids that combine elements of multiple main genres, like psychological thrillers.