Tempering gives chocolate its glossy finish and clean snap.
Chocolate tempering controls the formation of stable cocoa-butter crystals. Chocolate is carefully heated, cooled, and brought back to a working temperature so the preferred crystal form develops while unstable forms are reduced.
Properly tempered chocolate looks shiny, breaks with a crisp snap, and releases cleanly from molds. It also melts smoothly in the mouth. If chocolate is cooled without controlling its crystal structure, it may appear dull, soften easily, or develop pale streaks and patches.
Tempering is separate from fermentation, roasting, and conching. Fermentation develops flavor in cacao seeds, roasting adds further flavor, and conching refines texture. Tempering happens later, usually when chocolate is being prepared for molding, coating, or decoration.