The function modifies the HSV channels, which means that you can change hue, saturation and brightness separately.

At first the selected channels are scaled by the amplify value. E.g., set it to 200 and enable only the brightness checkbox to double the texture's brightness.

The Transformator replaces one channel value with another one to create interesting effects.

For instance you have a Perlin Noise texture and apply the Fractal transformation to it. This way you get a stone-like pattern. You are invited to experiment here.