The Differences Between Teaser Trailers and Theatrical Trailers

Teaser trailers differ from the main theatrical trailers in many ways theses include:

1. The length of the trailer; the length of a teaser trailer is often far shorter than the theatrical trailer due to the fact its only supposed to show snip-its of the movie so that it titillates the audience into wanting to see it. 
2. Teaser trailers give out less information related to the narrative than a theatrical trailer might. Theatrical trailers will often cover everything you need to know without giving the whole plot away. For example, the theatrical trailer will introduce you to the characters, the plot and confirmed release dates/age ratings, whereas the teaser may not even do any of those but just do enough to spark your interest in the movie without relaying much information.
3. Commonly among well known movies, such as Twilight or The Hunger Games, the teaser trailer is released before the theatrical trailer; in some cases they could be out even a year in advance.Of course this is all part of the film companies marketing strategy to build interest in their product, as part of it they may release more trailers, each with different content, over that long period before the final theatrical trailer and eventually the actual movie.