'Cacao' refers to the dried and fully fermented seeds of Theobroma cacao, a tropical tree native to Central and South America. These seeds are used to produce cocoa and chocolate products. The term can also describe the tree itself, and the food products made from its seeds, which are rich in fat and have a complex flavor profile that ranges from bitter to sweet.
The word 'cacao' comes from the Olmec word "kakaw" which was used by ancient Mesoamerican cultures to refer to the cacao tree and its seeds. It was later adopted into Spanish as "cacao," which has influenced its usage in English.