What is a Teaser Trailer?

After researching into Teaser Trailers, via Wikipedia as well as watching them online, I have noted the conventions of what I believe a teaser trailer does for an audience. Some basic facts are...

• Firstly they are usually between 30-60 seconds in length.
• They can contain little, if any actual footage from the film. This is often because they are made whilst film is still in production so instead they may feature alternate scenes or scenes created specifically for the teaser.
• The teaser trailer is part of an entire campaign and is used as a tool to start of the full blown-campaign.
• They create hype around the movie they are advertising, they act as a device of intrigue. To achieve this they often contain puzzles, hints or clues as to the narrative of the film. This can be done with text, clips, voiceovers, images, etc.