The Gizmo is used to capture the Landscape's height data that can then be used. This enables you to easily move parts of your Landscape, import height data from an existing heightmap, or to export
your height data to a heightmap file that can be used with an external program, like World Machine.
In these examples, the gizmo bounds have been scaled around a painted region that is to be captured, then the gizmo is positioned to another part of the Landscape, and, lastly, it's pasted onto the existing Landscape.
To learn how to use the gizmo, you can read about the gizmo tool here.