Light is that portion of the electromagnetic spectrum that we can see with our eyes. Roughly, you can see radiation from wavelengths beginning around 400 nm in the violet to around 700 nm in the far red. Radiation in the wavelength region just beyond 700 nm is called infrared while that in the region just below 400 nm is called ultraviolet. If you remember your Latin, this terminology may seem backward. Hue is the main color specified by the dominant wavelength.
Saturation is the purity of color.
Brightness is the overall intensity of the light. Lightness is the reflectance of a surface. These are the three primary colors of light. We can mix these primaries additively to get other colors. That is, purple is a saturated magenta.