The pages that contain a sorting number are listed as ordered pages. These pages are automatically listed in the (main) navigation. On the overview they are listed in the left column.
The unordered pages are not included in the navigation - but are still included in the sitemap or search results. The unordered pages are listed in the right column.
You can filter the pages by Status (public, invisible, private, draft) and language. In addition, there is the search field.