Parts in films refer to the various roles that actors and actresses play in a movie. These roles can range from the lead character to a minor supporting role. The term 'roles' is often used to describe the different parts in films, as each actor or actress has a specific role to play in order to make the film successful. Roles can also refer to the characters that are featured in a movie, such as the protagonist, antagonist, and other characters that are important to the story.