(written from a Production point of view)
A trailer is a short promotional tool used to preview a film or television show, usually with selected clips from the production.
Trailers might occasionally include scenes later deleted from the movie or created especially for promotional purposes, as was for example the case with Star Trek VI: The Undiscovered Country, Star Trek: First Contact and Star Trek.
- Star Trek: First Contact - Early trailers were released before much of the film was shot, and thus relied on footage from Star Trek: The Next Generation and Star Trek: Deep Space Nine.
- Star Trek - a specially-shot teaser showed the new Enterprise under construction, with a welder working on it.
- Star Trek Beyond  - This trailer was reported to be ill-received, with even co-writer and actor Simon Pegg adding to the criticism, and stating that it was not like the movie.   The second trailer was released online following a fan event on 20 May 2016.
- Star Trek: Discovery - A trailer showing images from previous Star Trek series and early behind the scenes footage was released on 31 January 2017. 
- Star Trek: Discovery - A trailer for the second season of Discovery was released at the 2018 Comic-Con on 20 July 2018 featuring a song by Lenny Kravitz.