A genre is a category of artistic works defined by similarities in form, style, or subject matter. The document discusses several common film genres including action, comedy, horror, thriller, sci-fi, and romance. It also mentions hybrid genres that combine elements of multiple genres, such as rom-com and action comedy. Thrillers specifically use suspense, tension, and excitement as their main conventions and tend to be fast-paced with plot twists and cliffhangers. Common thriller subgenres include psychological thriller, crime thriller, and mystery thriller.