This tab contains a list of page templates that use the currently edited shared layout. This means that any changes made to the layout will be applied to all of these templates. Templates that use a custom page layout are not included, even if they were created as a copy based on the current shared layout.
Clicking the Edit () action next to a template opens a new window where the properties of the given page template can be configured.
More resources can be found in Developer's Guide -> Development -> Web development overview -> Portal engine development.