Genres are categories of films like thriller, crime, horror, comedy, romance, and sci-fi that share common themes and symbols allowing audiences to recognize the type of film. While genre boundaries can be flexible, audiences develop familiarity with genres through repeated exposure, enabling directors to subvert expectations. Popular genres like horror films center around a scary plot and threatening characters, while westerns typically feature cowboys, horses, guns, desert settings, standoffs between two people, and depictions of American frontier life.