It puts at your disposal several ranges of color, derived from the current A color.
• Some luminosity variations based on the A color.
• Some saturation variations based on the A color.
• Some chromatic variations based on the A color (the Step option allows to adjust the chromatic variation).
If the Lock button is checked, the color boxes will stay the same whatever you do.
If the Lock button is not checked, the color boxes are automatically refreshed if you change the A color. (A simple click on a color of the Color Variation panel will change the A color into the one you have chosen)