Cinnamon, as in true Cinnamon, is Cinnamomum verum, also known as Cinnamomum zeylanicum, and is grown mainly in Sri Lanka where it's a native species and, other than in Sri Lanka, is not commonly sold in the rest of the world. What y'all know in the rest of the world is a close relative which is also sold as cinnamon, but which is more accurately called cassia, or Cinnamomum cassia.
Most people can't tell the difference between the two by taste or by looking at the powder, but the quills do have a distinctively different look. The bark of Cinnamomum cassia is much thicker than the bark of Cinnamomum verum. There are other important distinctions as well, such as the health benefits. A lot of memes have gone around the past year touting the health benefits of cinnamon, but are the health benefits from consuming Cinnamomum cassia or are they from consuming Cinnamomum verum? Best do your research before you take too much of the wrong one.
There's another interesting distinction. For me. Cinnamomum cassia makes me ill. Cinnamomum verum does not. And, since I can't tell by looking at the powder whether the cinnamon is actually cinnamon or if it's cassia masquerading as cinnamon, I've been buying my cinnamon, true Ceylon cinnamon, in Sri Lanka and bringing it back to Singapore with me.
Here we have a photograph of a large quiver of cinnamon (not cassia, but true Ceylon cinnamon) standing about three feet or so high. This was in a building on the grounds of a Buddhist temple in Colombo, Sri Lanka.