White chocolate has approximately 15% milk solids, a maximum of 55% sugar, and at least 20% cocoa butter.
Semisweet chocolate lies in between bittersweet and sweet dark chocolate, with at least 35% of its weight coming from cocoa solids.
The FDA states that bittersweet chocolate must have at least 35% cocoa, but the majority of bittersweet bars have 50%, and some have as much as 80%.
As the name suggests, unsweetened chocolate is pure chocolate liquor composed only of ground cocoa beans.
The most common kind of chocolate is probably milk chocolate, which is really just 10-40% cocoa combined with sugar and milk.
The most popular recipe using this type of chocolate is for German Chocolate Cake, a rich cake with three layers of chocolate cake, gooey, sweet frosting in the middle, and coconut and pecans on top.