The difference between a trailer and teaser.

The difference between a teaser trailer and a theatrical trailer is that a teaser trailer is designed to give you a small insight of the genre and film without giving too much of the story-line away. However a theatrical trailer is longer and normally includes more of the narrative story in the trailer with more references to the main characters and plot.

Here is the teaser trailer for 'Silent Hill'

Here is the theatrical trailer for 'Silent Hill'

As you can see, the second trailer is much longer and includes more narration, more an introduction to the characters, longer lasting shots, location shots, captions to match the trailer, dialogue and more of an insight into the film itself.