Types of Chocolate
Bittersweet & semisweet chocolate must contain at least 35 percent chocolate liquor. The chocolates in this category are manufactured with such a variety of mixtures of added cocoa butter, lecithin and vanilla, that their characteristics differ from brand to brand. In general, European companies label this chocolate as bittersweet or dark, while American companies refer to this chocolate as semisweet. There are no standard, technical distinctions between the two chocolates. In general, bittersweet chocolates will carry a stronger chocolate flavor.
Extrabitter chocolates (aka super-dark chocolates) are relatively new. They are generally available in bulk for professional chefs, although a few are being marketed to the consumer in bar form. These chocolates will pack a considerable chocolate wallop, but do not casually substitute them in recipes calling for semisweet or bittersweet chocolate.
Milk chocolate, America's favorite chocolate delivery system, is milder and sweeter than dark chocolate, and lacks its subtlety. A good milk chocolate strikes a balance between the milk and cocoa — the milk should not mask the cocoa flavor. It should melt in the mouth without a greasy feel. Because of the milk component, it is intolerant to heat, and therefore difficult to cook and bake with.
Unsweetened chocolate (sometimes called bitter, baking or plain chocolate) is chocolate liquor. It should not be confused with bittersweet chocolate.
White chocolate contains no cocoa solids. It is not labeled as "chocolate" in the United States because it does not meet the U.S. Standard of Identity's criteria for "chocolate." Instead, it is sold as "white confectionery bar" or "summer coating." However, the FDA is expected to issue a new standard on white chocolate, determining that a product with a minimum of 20 percent cocoa butter can be labeled as white chocolate.
Source: Chocolate Passion by Tish Boyle and Timothy Moriarty (Wiley).