To access the TerrainThe landscape in your scene. A Terrain GameObject adds a large flat plane to your scene and you can use the Terrain’s Inspector window to create a detailed landscape. More info
See in Glossary painting tools, click on a Terrain object in the Hierarchy window and open an InspectorA Unity window that displays information about the currently selected GameObject, asset or project settings, allowing you to inspect and edit the values. More info
See in Glossary window. In the Inspector, click the Paint Terrain (paintbrush) icon to reveal the list of Terrain tools.
The Terrain component provides six distinct tools:
2019–10–22 Page amended
Updated screenshot to match the new UI and added the Paint Holes tool.