This node is for using the Cinema 4D's "Gradient" shader. It should not be confused with Octane's "Gradient Texture", because their functions are different, even though their names are identical. We have already described Octane's Gradient Texture here. You can read what the C4D Gradient Shader is and what it does in the Cinema 4D help file, or you can go to this link for further information.
how to use
Open the Node editor and prepare the setup as you see in the picture below. In this simple setup C4D gradient connected Diffuse channel of the material. You can use this gradient some of the native Octane textures such as Turbulence, Marble etc. In fact, you can use Gradient on all Octane Nodes that have "power" and "texture" slots. This tool works very well in Octane. If you set the texture resolution based on your scene structure, you can work very efficiently. Remember that all the C4D textures converted to octane, so it wisely.