Some theme features are based on child pages, which are very flexible and easy to use. Child pages are often called sub-pages, too.
For example, the ‘Business Front Page’ template of the Air Balloon theme displays all its child pages in a slideshow using the featured images of the child pages.
Set a Parent Page
You can create a child page by setting a parent page on the ‘Edit Page’ screen which you find on your WordPress admin panel → Pages → All Pages → Edit Page or when you create a new page.
You should see a metabox ‘Page Attributes’ below the ‘Publish’ metabox, where you can set the Parent of this page. If you do not see the ‘Pages Attributes’ metabox, check your screen options.
If you set a parent page, the edited page will automatically become a sub-page of the selected page. Your pages are now arranged in hierarchies. There is no limit how deeply you can nest your pages.