Differences between a teaser trailer and the main theatrical trailer

A teaser trailer, or 'teaser' is a short advertisment for an upcoming movie etc. It is usually released a long time before the film is due to appear in cinemas in order to 'tease' the audience. Teaser trailers, unlike theatrical trailers, only include small, if not any, amount of footage from the actual film and can usually last between 30-60 seconds. Teaser trailer are usually designed for big-budget, popular film as the purpose is not so much to advertise the content of the film but just to let the audience know that the film is coming up in the near future and to add excitment. Teaser trailers are usually made while the film is still in production and therefore can contain alternate scenes to what will be seen in the movie. Some production labels such as Pixar even include different scenes in their teaser trailers deliberately in order to give the audience a taste of the film but to not spoil it.