The HSL color space is designed to be intuitive and follows the model of mixing paints. An artist preparing a color for a painting, first selects a hue (pure color pigment). He may then add black or white paint to arrive at the desired color. Adding white serves to wash out the color. In technical terms, we say this affects the saturation of the color. The artist may then adjust the brightness by adding black paint. This affects the amount of light reflected by the pigment. We call this the luminosity.
Saturation ranges from zero (white) to one (pure color - no added white). Luminosity ranges from zero (black) to one (pure color - no added black). Hue ranges from zero to one. The diagram below gives an indication of where several colors occur in that range:
