Have you ever wondered why Cacao/Cocoa can be spelt in two different ways?

They say these terms are often used vice versa. However there is an important difference between them.

Basically, cacao refers to the seed of the Theobroma cacao tree and is the the name for the unprocessed beans. These can be eaten raw, but they are very bitter.

Cocoa on the other hand is the name for the processed beans of the cacao tree and the main ingredient for chocolate.

Source: The Little Book of Chocolate