text: why are the movie previews  called 'trailers'?   film trailers are film advertisements. they are shown before the screening of another movie, at a cinema where the films will be exhibited, as well as in the lobby and on internet. they are more formally known in theaters as previews of coming attractions. the term "trailer" comes from their having originally been shown at the end of a film programme. although that practice did not last long, due to patrons tending to leave the theater after the films proper were finished, the name has stuck.