Design > Site Pages Tab Overview
The Design > Site Pages Tab in the admin is where you will create and edit your site pages for your frontend website.
Clicking the Blue Plus icon on the Site Pages Tab will cause the browser to navigate to a new page that allow you to create a new site page or landing page for you website.
Clicking the Red circle with an X icon on the Site Pages Tab will delete the site page in that row.
Clicking the hyperlinked "Edit" button will cause the browser to navigate to the edit that site page.
For an overview of the Design tab Click Here