Type:
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You can choose from 3 different noise types: grid, perlin and cell.

Metric:
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This controls the method used to create the noise cells. Distance gives softer, more rounded cells, while Manhattan gives more rectangular cells.

Frequency:
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This determines how 'tiled' the noise is. As the frequency is increased, the cells/features of the noise get smaller and more numerous. It works the same as increasing the max values in the texture_projection node, but allows you to have only one such node driving different Whirlys, each with different frequencies. This way you can easily get a 'Layered' effect.

Jitter:
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This controls how much the noise cells are displaced from their normal position. At small jitter values, the cells are arranged in a regular grid like pattern that becomes more and more distorted as the param is increased.

C1,C2,C3:
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These 3 params work together to control how each cells is rendered. They work additively, so for best results, either use one alone (setting the other 2 to zero) or combine them in +ve / -ve way. eg C1 = 1.6, C2 = -1.2 etc.

Clamp:
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Often if you are using large C1/C2/C3 values, the output of the shader can go beyond 1.0 This doesn't matter for bumps, but for diffuse, this will cause the material to which the shader is attached to become a light emitter ! So by checking this option, you can force the output to be contained within 0 to 1. This can also be used with bumps to get a 'sheared' effect at the top or bottom of the bump.

Coord:
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The shader needs a texture coordinate generator attached to this to work properly.