Whether you import terrain into SketchUp or create your terrain completely from scratch, you likely need to sculpt your terrain or make minor adjustments. With specialized Sandbox tools, you can create berms, ponds, terraced landscapes, and so on. The Smoove tool enables you to model hills and valleys on a TIN (triangulated irregular network). With the Add Detail tool, you can split a selection within a TIN into smaller triangles so that you can model detail where its needed.
Terrain is important to many SketchUp modelers: Your building needs ground to stand on, or maybe you're modeling the ground itself to create a landscape. But wait. SketchUp's Sandbox tools - the tools you use to model terrain - can also create forms completely unrelated to terrain. How can terrain include all these other possibilities?