What is a teaser trailer?

From what I have learnt from the teaser trailers I have analysed is that the structure of a teaser trailer is to keep as much of the storyline hidden as possible because that needs to be saved until the official trailer is released closer to the time. Its purpose is to add hype to the upcoming release and to just 'tease' the audience to make them aware of the film. They are often shown up to a year ahead of the film actually being released and are normally only made for big budget films. The majority of the teasers I have watched contain little of the actual footage from the film as possible because of how early on in the making of the film they are released, this often means the teasers contain alternative footage that may not be used in the actual film. They are usually around a minute and a half long, enough time to get the audience’s attention and fulfil its purpose without giving away too much information.
Because of the two different genres of the teaser trailers there are hardly any if no similarities between them apart from Paranormal Activity and The Strangers. They both target a different audience, although the age group targeted could be similar between all three. The connotations and conventions used in The Strangers and Paranormal Activity are also similar, the camera loosing signal and the old footage of The Strangers create the same sense of fear between the trailers. They all feature small amounts of footage from the actually film and none of them give away much of the storyline, The Strangers gives away the most out of the three however because from the footage shown you can have an idea of what is going to happen. It is a very typical horror film, with a couple being harassed by being in the wrong place and the wrong time.