Cacao refers to the raw bean, or an unprocessed version of it (cacao nibs are crunched up versions and cacao powder is ground cacao beans). This is often known as the healthiest form of chocolate that you can get, but it is also quite bitter in taste. The cacao beans can be eaten raw or roasted and are most common in chocolate-producing countries.
A lot of people claim that white chocolate is not even real chocolate, and that is actually true. White chocolate is made from sugar, milk, and cocoa butter, without any actual cocoa solids. This is why it is white in appearance instead of the typical brown color of chocolate. White chocolate, by law, must have at least 20% cocoa butter, 14% milk, and a maximum of 55% sugar. This type of chocolate is often enhanced with flavors like vanilla to complement its natural taste.