Gradient Ramp
The Gradient Ramp node can generate the color output for the input greyscale texture based on the knots and their interpolation that you assign for the range of input greyscale values. Each knot of the gradient setup can also be textured using other node connections.
The Gradient Ramp is very useful to create the colored output based on the greyscale inputs from Noise, Flakes, Random or Pattern node.
By default the Gradient Ramp understands only the values from [0..1] range of Input Map and maps them to the specified colors where the black input value is mapped to the first (left) knot and white input value is mapped to the right knot. In case the input values belong to the different value range then this range needs to be specified in the Input Min / Max values. Remap node has the same functionality.