Understanding The Difference Between a Trailer and an Opening Sequence

Movie Trailer
A movie trailer is made to create interest and a want to watch a film, it will appeal to the audience who favour that genre of film. A trailer also advertises the film, showing all the best bits without any spoilers, creating curiosity in order to make the audience think in more depth, and, fill in the gaps. This advertisement shows actors, directors and production companys which enables the audience to have an idea of what to expect based on the stereotypes of those assets.
The main conventions of a movie trailer: Release date, Age rating, voice over, short-sharp shots and websites.

Opening Sequence
An opening sequence creates interest by forcing the audience to the mood of the film, this absorbs them into the world of the film. If the opening sequence isnt relevant then it will have no effect on the audience and as a result wont provide them with the neccessary information to keep the audience curious.
The main conventions of an opening sequence: Slow shots, credits, and, clues.