The HSB (Hue, Saturation, Brightness) color wheel chart is a tool used in color theory to represent colors based on their hue, saturation, and brightness. It is characterized by concentric circles, where each circle represents a different brightness level, with hues evenly spaced along the circumference. The chart helps in understanding color relationships, such as complementary and analogous colors, and is widely used in graphic design, art, and photography.