Deep Linking basically means linking to internal pages of your site directly. Standard HTML websites do this naturally so no further action is required. If your site is built using Flash or AJAX it’s a different story though. Why?
In order to link to a page you need a unique URL or webpage address. Standard HTML sites have this since each navigation link will reload the browser window with new content. So each sub page is on it’s very own page with its own address.
Flash or AJAX sites work differently. They usually consist of just one single file or script that loads new content directly without reloading the browser window. It renders a very slick user experience but the address in the browser does not change when sub page content is loaded.
Deep Linking techniques use Java Script to change the address when new content is loaded enabling visitors to bookmark, share or email individual subpages.
As an example, the Kinetik site uses deep linking. Just click on any of the black navigation items above and explore. See how the address bar changes without reloading the browser window.