Black can be defined in a few ways. It does not emit any color, nor reflect any light and thus appears black to the human eye. Black can be both the absence of color and a blending of the three primary colors of red, blue and yellow to create a shade resembling black to the human eye.
Black surfaces absorb heat. The photons that hit the surface are absorbed; and since the First Law of Thermodynamics states that energy can neither be created nor destroyed, the photons excite the surface particles of the black object, causing them to move faster. Fast moving particles are warmer than slow moving particles, so black objects are hotter than other colored objects.
White is all the colors in the spectrum. When white light is shined through a prism, the colors that make up the light are separated into their individual colors. White also reflects photons, making it a fabric that is cooler to wear in desert and other hot climates. Thus “never wear white after labor day” rule doesn’t really apply in the Southern hemisphere.