A trailer (also known as a preview or coming attraction) is an advertisement or a commercial for a feature film that will be exhibited in the future at a cinema. The term "trailer" comes from their having originally been shown at the end of a feature film screening. That practice did not last long, because patrons tended to leave the theater after the films ended, but the name has stuck. Trailers are now shown before the film (or the A-movie in a double feature) begins.