In Response To 'Re: About the Demonstrations'
The Demonstrations programs are based on the Manipulate function. Start by looking at the documentation for Manipulate.
Click the ">>" hyperlink at the end of the output from
in Mathematica or go to
in your web browser.
After you have read that and run the examples and modified them to see what happens, move on to the dynamics tutorials linked to from the bottom of the page.
Dynamics can get very complicated. Expect to need more than a quick skim of the documentation to get the hang of it.