Its all about "Editable Regions" Contribute works off "templates". The designer set's up the templates like regular web pages, then saves it as a .dwt (dreamweaver template) file extension. I suppose it would be possible to write the page without dreamweaver, but not easy.
I have a video on my page
"Get Started with Contriubte CS3". About half way down there is a link for "Creating Dreamweaver Templates for Contribute CS3" A nice little video that should answer most of the questions you may have.