In larger sites, it can be difficult to keep track of the proper URL alias to use for a given page (the alias ideally should include all the parent pages in the hierarchy). To better manage the URLs, your webmaster can create Site Sections using the Site Section taxonomy terms, as explained further below.
Each of these taxonomy terms represents a particular section of your site, within which pages will share a common URL. Site sections can be nested within each other as well. If you choose to use this method, you should pick the appropriate Site Section from the dropdown on the node edit page rather than entering a URL manually. The URL will be automatically generated for you to include the correct path.