Teaser Trailer

A teaser trailer, or just teaser, is a short trailer used to advertise an upcoming film, television program, video game, or product.
Teasers, unlike typical theatrical trailers, are usually very short in length (between 30–60 seconds) and usually contain little, if any, actual footage from the film. Sometimes, it is merely a truncated version of a theatrical trailer. They are usually released long in advance of the film they advertise. One of the reasons for the name "teaser" is because they are shown usually a long time (one or one and a half years) before the movie comes out, so as to "tease" the audience.

http://www.youtube.com/watch?v=GRIVaXrgddg

Above is the link for the teaser trailer for Dawn of the dead (2004), the link below shows the full trailer for the film

http://www.youtube.com/watch?v=G6LPWtaI61I

when compared the teaser trailer shows alot of the usual aspects of a teaser trailer, with it being fairly short and not giving much away, whilst the main trailer is a lot longer and goes into a lot more detail.