Difference between a "teaser" and a "movie trailer"

Teaser trailers are usually just an insight into the film, and is released before the main/theatrical trailer. It gives the audience a brief insight into the film, but without giving much away, and often do not include footage or information which can directly relate to the film.





For example, the comparison between these two spiderman trailers is that, because of the popularity of the spiderman franchise, it is important for them to release a trailer to increase audience interest. It gives a small taste into the next film, and creates popularity by leaving the audience in suspense.