The five main types of chocolate are milk, unsweetened, white, bittersweet, and semi-sweet. The types of chocolate are based on whether the chocolate is made of cheap and ordinary cacao beans or expensive cacao beans that have a great scent. It is also based on how much cacao they contain. The price is also based on the way the beans have been roasted and form what they add into the mixture.

One main type of chocolate is white chocolate. White chocolate is made of cocoa butter, sugar, milk, emulsifier, vanilla, and maybe other additives. This chocolate does not include any of the non-fat ingredients from cacao, causing an off-white color. The percentage of cocoa solids in white chocolate is so low that some countries do not even consider it chocolate. This chocolate has a pleasant taste. Pastry chefs and chocolate lover could use white to eat alone, make Chocolate Mousse, Panna Cotta, and other fine desserts.
Another type of chocolate is milk chocolate. Milk chocolate tastes sweet. Milk chocolate usually contains 10-20% cocoa solids. Cocoa solids are made of cocoa and cocoa butter. It contains more than 12% milk solids, that is why it is called milk chocolate. Milk chocolate is not usually used in baking other than in cookies.
Dark chocolate is another one of the five main types of chocolate. It is occasionally sweetened, if so not very sweet. Dark chocolate is high in cocoa solids. It usually contains around 0% milk solids, but it can contain up to 12%. Dark chocolate has the possibility of being sweet, semi-sweet, bittersweet, or unsweetened.

Another category for chocolate is semi-sweet chocolate. Semi-sweet chocolate is the original (classic) dark chocolate that is used for baking. It is often found in recipes for cakes, brownies, and cookies. It often has 40-62% cocoa solids. It can replace semi-sweet chocolate. Sometimes semi-sweet and sweet dark chocolate taste so similar it is hard to tell the difference. The only difference is that sweet dark chocolate has 35-45% cocoa solids.
A sweetened dark chocolate is bittersweet chocolate. Bittersweet is another one of the main chocolate types. It contains at least 35% cocoa solids. The better varieties of bittersweet chocolates have 60-85% cocoa solids. It is high in its cocoa content and low in sugar, giving you a flavor that is rich and intense. Bittersweet chocolate is often used in baking and cooking. When a recipe specifies bittersweet—do not substitute! European bittersweet chocolate has the best quality.
The last of the five main types of chocolate are unsweetened chocolates. This chocolate is bitter. It is only used for baking, and it is not good to eat on its own. Unsweetened chocolate should only be used if a recipe says to us it. It is almost made of 100% cocoa solids, and half of it might be cocoa butter (fat).