Besides its primary content, a web page contains other content such as site branding (site name, slogan, and logo), navigation aids (menus, links, and icons), formatted text and images. Each theme provides a set of named regions, such as Header, Content, and Sidebar, where site builders may choose to place their content.
The available regions depend on the theme design. Only the Content region, which contains the primary content, is required; others are optional.
Regions can be displayed by navigating to the Structure Block layout and clicking the Demonstrate block regions (GovCMS 8 UI-Kit Starter) link.