The Gaussian uses a Gaussian distribution spectrum.
Figure 1: Gaussian Spectrum parameters
Wavelength - The mean wavelength approximation between 380 nm - 720 nm (with a range from 0 - 1). Lower values appear bluish, and higher values (around 700 nm) appear reddish.
Width - When set to 0, almost no color is visible. When set to 1, the color spreads thin over a large space, and the texture appears faint.
Power - The texture's brightness.
Figure 2: The Gaussian Spectrum node connected to the DiffuseAmount of diffusion, or the reflection of light photons at different angles from an uneven or granular surface. Used for dull, non-reflecting materials or mesh emitters. input on a Diffuse materialUsed for dull, non-reflecting materials or mesh emitters. node.