Sri Lankan cinnamon, most often referred to as Ceylon cinnamon, is the only type of cinnamon that is 'true cinnamon'. There are other species that are closely related but these are known as Cassia. Ceylon cinnamon is typically more expensive than any of the other varieties of cassia and is said to have more health benefits. It is often difficult to see the difference between cinnamon powders that have been made using true cinnamon versus the different cassias. I've found that Ceylon cinnamon powder has a lighter colour and a more woody texture. In terms of flavour, Ceylon cinnamon is much gentler and is beautifully aromatic and slightly earthy. The powdered cinnamon made from cassia is more spicy and stronger in flavour.
Ground Cinnamon is perhaps the most common baking spice. It is used in desserts, bakery goods or mixed with other ground spices to create different blends. In general, cinnamon is a great spice to use during the winter months for its lovely warm and fragrant flavours. Also great added to teas with a chunk of fresh ginger.