trailer

A trailer is a short publicity film, preview, or advertisement composed of short excerpts and scenes from a forthcoming film or coming attraction, usually two-three minutes in length. Often presented at the showing of another film. Historically, these advertisements were placed at the end of a newsreel or supporting feature and so "trailed" them, hence the name. Also commonly known as "preview(s)." Also, another name for the tail, a length of blank leader (strip of film), at the end of a reel. A "teaser" is basically a very short trailer (of 15-30 seconds in length) that only provides a few hints about the film (a Web address, a few bars of music, a quick sequence of images, specially shot footage, etc.).