The treatment is a useful document for you to start getting ideas together. It forces you to think in terms of what your story is going to be by summing it up within a logline and synopsis. Developing characters by simply deciding on names, personalities and characteristics helps with creating the script.
Many treatments can go into further detail by exploring the 3 act structure and writing in key scenes and how they develop.
A simple treatment for the film Bladerunner can be found to the left. This outlines a logline, characters and a synopsis. As you can see it has an overall idea of how the film is going to play out without having to write down a lot of information.
A copy of a treatment can be found here
You must make a copy of the document to your own drive.