I just think of it like photoshop...you have three layers, and you can chose how to blend them, and the noise and phase dialogs are like applying filters to the image. Noise is the base texture, the filter dialog effects the alpha channel of that noise, and the phase effects the internal structure of the noise. Phase is very important. It's how you get "fluidic marble" or wavey bricks, because it adds a secondary pattern to the noise pattern.