Trailer Terminology with definition

A trailer is a series of selected shots from a certain film that is being released in the near future. Trailers are used to entice the public so they usually use some of the best shots contained within the film: albeit explosions for an action film, or the funniest scenes for a comedy, to make the film seem great and to entice the audience. A trailer has a time limit which it cannot exceed in order for it to be shown in theaters which is two and a half minutes. Once a year however, studios or distributors are allowed to exceed this time if they feel it is necessary for the film.

Plot Summary:
Many trailers have a "three act structure" similar to a feature film. Act 1, the beginning, starts outs with establishing the premise of the story. Act 2, the middle, drives the story further and usually ends with a dramatic climax. Act 3 usually features a prominent piece of "signature music" which is usually recognisable. This then leads up to the last act which is almost always a visual montage of memorable moments which will feature in the film but may also contain a cast run of famous actors that help sell the film.

Voice-over:
A voice-over narration is commonly used in trailers in order to set up the premise of the movie and provide explanation when necessary which will make the trailer easier to comprehend.

Music:
Music is a vital part in a trailer because it adds tone and sets the mood. The music is usually not from the film itself because it has not entered post-production yet and the score has not been composed. Therefore, the music used in the trailer can be music from the score of other movies, popular music which is chosen to match the tone of the film, "library" music previously composed to be used in advertising, specially composed music or songs such as knock-offs of recognisable songs.

Cast, crew, and studio information:
A cast run is a list of the stars that appear in the movie. This can also be the same for the director or producer if they are well known and have made successful movies throughout their career. A billing block is used in the majority of trailers which shows a list of the principal cast and crew who worked on the movie. This can appear either at the start or end of the movie and tends to be the same list seen on posters or print publicity materials of the film. Studio production logos are usually featured at the beginning of the trailer whereas in the late 1970's, they were only put on the end of the trailer.

Technical elements:
Video resolution: Trailers are usually presented in the same way as the feature film, whether it is in 35mm film or a digital format. Improvements in internet connection means that many trailers can be distributed at resolutions up to 1080p HD quality.
Sound Mix: most movie trailers are presented in Dolby Digital or another multichannel sound mix. Stereophonic sound enhances any sound effects or music, which makes it one of the focus points of modern trailers.