Distance blending, is blending between 2 different values based on the object distance. In the example screenshot below, as you move closer, pixels of the object turns red, and as you farther, they go blue.
Basic Shader Setup
Higher values in falloff makes the transition sharper.
There are variety of use case for distance blending. It is most commonly used for terrains, as it hides tiling fairly well.
Node setup for the above example: