The stunning header is an area between a page header and content, which contains a page title, breadcrumbs, and additional text.
Stunning header appearance is controlled via Customize > Stunning header section. It has 5 subsections for different page types, namely:
Each section allows you to control the appearance of the page title section for the chosen subsection and adjust its design and content.
The options are the same as the following for each subsection:

Let's review these options in detail.
Here you can manage stunning header elements visibility:

If you enable Showing title on the option below, you can edit the stunning header title and its description.
If you don't want to add any custom titles, the title of the page will be shown.
Text color
This option lets you choose the color of the page title, breadcrumbs, and description if there is any.
Here you can choose the alignment of the page title, breadcrumbs, and description.
Here you can select a custom background color using a color picker. 
Here you can upload your custom background image.
If needed you can upload a wide image that will be displayed under the title and breadcrumbs.
This is space from the page title to the top and bottom borders.
It is possible to customize stunning header styling and components inside each page. These settings are higher by priority than ones in Pages. Choose the Page you want to edit, click "Edit Page" or go to Customize> Stunning Header sections.



Refer to this tutorial to read more about available options for a stunning header for a separate page Stunning header.