Ceylon cinnamon, sometimes called "true" cinnamon, has a lower volatile oil content which makes it more subtle with a sweeter flavor.  Pairs well with milk, cream or custards.  Saigon cinnamon, whose volatile oil content is higher is fiery, rich, fragrant and perfect with chocolate or in cinnamon rolls.

Cinnamon is spice obtained from the inner bark of several tree species.  Cinnamon was the  traders best kept secret in ancient times.