Workspaces are special non-public pages where you can prototype your theme or plugin using workspace modules. These modules represent various components in WordPress development such as Custom Post Types and Nav Menu Locations as well as styling concepts like stylesheets and typography styles. As you add Workspace Modules to a Workspace page, they will simulate that object in code so you can test how your site will work. All of your workspaces are available from admin bar at the top of the page. When you're finished setting up your modules, you can export the PHP and CSS code from the Workspace -> Export admin page.