URL mapping allows portal administrator to create constant user friendly URLS and map themt to portal pages. As administrator create the URLs they can define human readble names for them.
Clicking on a mapped URL from outside the portal takes the user straight to the desired page in the case of pages which are accessible without login to the portal. In the case of pages which require login the user is prompted for user ID and password. After successful login the portal takes the user directly to the desired page. However, this works only if portal security is enabled. Otherwise the portal redirects the user to the portal Welcome page.