"Portal Pages" is where the web pages used in the Portal are listed. There are these types of Portal Pages:
List View Page - pages that show a list of items. The list can be filtered by user, department, or other criteria.
New Form Page - pages for creating an item
Display Form Page - pages for displaying an item (list item, KB article)
Edit Form Page - pages for editing an item
Search Page - shows the KB article search page
Service Catalog Page - shows the Service Catalog page (optional)
The Portal Pages section will show what Portal Pages are configured for the type in the "Select Page Type" drop down. Use that drop down to switch between types of Portal Pages.
An existing page can be edited or deleted. The URL of the page can be copied for use in setting up menus or links.
The "New Page" button shows the screen to configure a new page. See the following sections to configure a Page for each of these Page Types: