The MaterialThe representation of the surface or volume properties of an object. Mixer mixes any two material types. It accepts any two material nodes and the mix may be controlled by a value, color, or texture. There are additional inputs for connecting a displacement map and custom AOVs which will be added on top of the materials being mixed.
In Figure 1, the Material Mixer mixes two 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. materials together using a Checks texture as the Mix Amount.
Figure 1: Mixing two Diffuse materials using a Checks texture as the Mix Amount