Chocolate Festival, Kiev, Ukraine

Dark chocolate is produced by adding fat and sugar to the cacao mixture. The U.S. Government calls this "sweet chocolate", and requires a 15% concentration of chocolate liquor. European rules specify a minimum of 35% cocoa solids. Dark chocolate, with its high cocoa content, is a rich source of epicatechin and gallic acid, which are thought to possess cardioprotective properties. Dark chocolate has also been said to reduce the possibility of a heart attack when consumed regularly in small amounts. Semisweet chocolate is a dark chocolate with a low sugar content. Bittersweet chocolate is chocolate liquor to which some sugar (typically a third), more cocoa butter, vanilla and sometimes lecithin have been added. It has less sugar and more liquor than semisweet chocolate, but the two are interchangeable in baking.
Unsweetened chocolate is pure chocolate liquor, also known as bitter or baking chocolate. It is unadulterated chocolate: the pure, ground, roasted chocolate beans impart a strong, deep chocolate flavor.