Version: 2019.4
Terrain Settings
Terrain Tools

Using Terrain at runtime

The Terrain system uses Unity engine resources to function correctly. Unity includes these resources in your Player build when you have at least one Terrain instance in a Scene that is part of the build. If you only create Terrain dynamically at runtime, make sure you include a Terrain component somewhere in your build as a placeholder. You can disable that Terrain instance (uncheck the box next to the Terrain name in the Inspector window), and put it in a Scene that your game or app doesn’t load.

Terrain Settings
Terrain Tools