According to Wikidedia Chocolate is a popular ingredient and is available in many types. Different forms and flavours of chocolate are produced by varying the quantities of the different ingredients. Other flavours can be obtained by varying the time and temperature when roasting the beans.
"Unsweetened chocolate is pure chocolate liquor, also known as bitter or baking chocolate, mixed with some form of fat to produce a solid substance. It is unadulterated chocolate: the pure, ground, roasted chocolate beans impart a strong, deep chocolate flavour. With the addition of sugar, however, it is used as the base for cakes, brownies, confections, and cookies.
"Dark chocolate is produced by adding fat and sugar to cacao. It is chocolate without milk as an additive. It is sometimes called "plain chocolate". The U.S. Government has no definition for dark chocolate, only "sweet chocolate", which requires a 15% concentration of chocolate liquor. Sweet chocolate is not necessarily dark chocolate as there is no restriction of milk in it. European rules specify a minimum of 35% cocoa solids.
"Milk chocolate is chocolate with milk powder or condensed milk added. The U.S. Government requires a 10% concentration of chocolate liquor. EU regulations specify a minimum of 25% cocoa solids. In the 1870s, Swiss confectioner Daniel Peter invented the process of solidifying milk chocolate using condensed milk, which was invented by Henri Nestle in the 1800s.
"Semisweet chocolate is often used for cooking purposes. It is a dark chocolate with a low (typically half) sugar content.
"Bittersweet chocolate is chocolate liquor (or unsweetened chocolate) to which some sugar (typically a third), more cocoa butter, vanilla and sometimes lecithin has been added. It has less sugar and more liquor than semisweet chocolate, but the two are interchangeable in baking. Bittersweet and semisweet chocolates are sometimes referred to as 'couverture' (chocolate that contains at least 32 percent cocoa butter); many brands now print on the package the percentage of cocoa (as chocolate liquor and added cocoa butter) contained. The rule is that the higher the percentage of cocoa, the less sweet the chocolate will be. The American FDA classifies chocolate as either "bittersweet" or "semisweet" that contain at least 35% cacao (either cacao solids or butter from the cacao beans).
"Couverture is a term used for chocolates rich in cocoa butter. Popular brands of couverture used by professional pastry chefs and often sold in gourmet and specialty food stores include: Valrhona, Felchlin, Lindt & Spr?ngli, Scharffen Berger, Cacao Barry, Callebaut, and Guittard. These chocolates contain a high percentage of cocoa (sometimes 70% or more) and have a total fat content of 30-40%.
"White chocolate is a confection based on sugar and fat (either cocoa butter or vegetable oils) without the cocoa solids. Technically white chocolate is not chocolate, because of the lack of cocoa solids."