"The Library of Congress Genre/Form Terms for Library and Archival Materials (LCGFT) is a thesaurus that describes what a work is versus what it is about. For instance, the subject heading Horror films, with appropriate subdivisions, would be assigned to a book about horror films. A cataloger assigning headings to the movie The Texas Chainsaw Massacre would also use Horror films, but it would be a genre/form term since the movie is a horror film, not a movie about horror films.
The thesaurus combines both genres and forms. Form is defined as a characteristic of works with a particular format and/or purpose. A 'short' is a particular form, for example, as is 'animation.' Genre refers to categories of works that are characterized by similar plots, themes, settings, situations, and characters. Examples of genres are westerns and thrillers. In the term Horror films 'horror' is the genre and 'films' is the form."