Every time a CONTENTdm page is loaded CONTENTdm reads the URL (visible in the Address bar of your browser) and uses the information found there to determine exactly what it is being asked to do, and how to display the results. With the exception of the Web Administration interface and the Acquisition Station every user interaction with CONTENTdm is really a matter of changing URL and displaying the results.
Here is a partial list of the options CONTENTdm determines from the URL:
The basic type of page to display (i.e. the browse page for a collection, the search page, the search results page, user preferences, etc.)
Which template to use.
If searching, which items should be displayed.
If browsing, which collection to browse.
Which fields to display in a search or browse (Image, Title, Subject, Description).