The Manage Pages area is designed to give you an overview and basic site-map of all the pages on your system.
It is a useful way to access pages or edit them instantly without having to figure out where they are located.
Hint: In your list of pages under "All Pages" it is possible to see the hierarchy of pages but looking at the » symbol. In the example below, you can see "Child Page" is a sub page of "Parent Page"
It is also possible to create new pages from this area.
Note: If you decide to create a page from here and you do not give it a location (i.e. a Parent Page and Section, or in the Side Menu) then it will be only accessible from this area.