How to write a Film Treatment?

Looking at different websites gave me an idea of how to start of when writing a film treatment.

http://www.lightsfilmschool.com/articles/treatments/index.html

This website generally describes what treatment is about, how long it should be and it explain what it is for.

http://www.beatsheetcentral.com/

This website is created by a screenwriter and a director, who explains the importance of the process which describes the movie  or TV episode.