My chef & mentor Kriss was always very particular about the difference between standard 'cinnamon' and 'true cinnamon', aka 'Ceylon cinnamon'. I'm afraid that if I don't make this clarification in conjunction with my last post, he'll channel up an evil spirit to come and yell at me in Michigan.
Technically, Cassia cinnamons, or Chinese cinnamons, come from the aromatic bark of an evergreen tree that is native to China and Vietnam. It has a higher oil content and produces a dark brown, thick rolled bark with a strong flavor and scent, with a bit of a harshness to it in large quantities. Most mass produced cinnamon sold in the US is of the Cassia variety, and is what most people in the states are familiar with. If you've ever walked passed a 'Cinnabon' store in an airport, you've passed through a cloud of cassia cinnamon-scented air.
'True cinnamon', on the other hand grows on shorter evergreen trees native to Sri Lanka and South India. It's paler in color and has a smoother, thinner bark that breaks easily in your hands. Distinguishable from Cassia in that it's flavor is more subtle, and the smell is much less sharp in your nose.
Although the trees are related to one another, they are quite different. It's worth tasting them side by side and considering them for different applications. I probably wouldn't use the cassia cinnamon for a delicate pastry, but my food memory of (and occasional longing for) cinnamon rolls wouldn't be saited with the delicate touch of 'true cinnamon'.