Teaser Trailers and Theatrical Trailers... What are the differences?

Teaser trailers differ from he main teatrical trailers in mnay ways theses include:

• Length, they're often shorter by about a minute or 2.
• They give out less information related to the narrative. Theatrical trailers will often cover everything you need to know. For example, the teatrical trailer will introduce you to the chracters, plot (Bruce Willis has to infiltrate a highrise building to save his wife and stop some terrorists) and confimed 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 withourt relaying much information. One of my favorites is teh teaser for Christopher Nolans final entry  into his Batman trilogy, The Dark Knight rises, shown below! You can see how simple it is, it doesn't give too much away yet leaves you wanting more.
• More often than not they're out way before the teatrical trailer is. In some cases they could be out even a year in advance! Of course this is all part of a clever amrketing strategy to build interest, 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 is released.