Function.

Function

A function is symbolized as a circle with one input slot (white circle) and one output slot (red circle). It applies one of the following mathematical functions to the input.
Absolute.
Strips the sign, leaving a positive value.
Clamp.
Clamps the input between a high and low value.
Invert.
Multiplys the value by -1. If used as the last transformation before output it effectively inverts the output.
Sine.
Applies the sine function to the value, trating the value as radians.
Mask.
Sets the output to one of two values based on whether the input is geater or less than a certain value.
No Operation.
Has no effect. It can be used to put the same noise through both sides of a combiner, or has a quick way to disable another function.
Rough Scale.
Scales the noise between two values. It's not 100% accurate hence 'rough scale'.
Erode.
A simple erosion simulation. Note the icon and preview does not work for this noise yet.
Terrace.
Applys a terracing effect, adding flat areas to the terrain.
Rotate.
Rotates the noise.
Craterize.
Applies a crater side shaped spline to the noise.
Splinify.
Samples the incoming nose and uses the results for control points in a spline patch.

The following table shows a few examples.

Absolute
Clamp
Invert
Sine
Mask
No Operation
Rough Scale
Erode
Terrace
Rotate
Splinify
Craterize