The Mix texture node mixes two textures together. In Figure 1, a Marble texture combines with a Checks texture that's using the Mix texture connected to the Octane material's DiffuseAmount of diffusion, or the reflection of light photons at different angles from an uneven or granular surface. Used for dull, non-reflecting materials or mesh emitters. component. The Amount slider balances the strength of the two textures (Figure 2).
Figure 1: A Marble and a Checks texture blended with the Mix texture
Figure 2: The node network used for the rendering in figure 1.