Teaser Trailers vs. Full Trailers

A teaser trailer is always shorter in length than the full trailer and they normally do not give such big plot indications as the full trailers.  This is to build audience interest and to keep them in suspense so they are more likely to want to go and see the movie when it is released in cinemas or on DVD or Blu-Ray.  Teaser trailers are usually released some time before the full trailer to generate audience hype and publicity and often teaser trailers can be a lot more 'action packed', featuring much faster paced action to keep the audience involved and the trailer down to a shorter length.  This also helps to build suspense.

Here is an example of a teaser trailer for 'Saw 3D':


And here is the full trailer for 'Saw 3D':