Starbucks tomorrow : “let me get 3 Grande iced brown sugar oatmilk shaken espresso, blonde ristretto shots, 3 pumps cassia dolce, 2 pumps sugar-free vanilla, cassia cold foam, cassia powder, extra cassia crunch, light ice, upside down, in a venti cup.”
The cinnamon in your cabinet is almost certainly cassia, which is a different plant.
Real cinnamon, the kind sold as Ceylon or true cinnamon, comes from Cinnamomum verum and it's grown mostly in Sri Lanka. Nearly everything sold in America as cinnamon is cassia, one of 3 related species grown in Indonesia, China and Vietnam. FDA does not require the label to tell you which one is in the jar, so most of the time it just says cinnamon.
You can tell them apart by looking at a stick. Cassia is one thick hard curl of bark that you could hit someone with. Ceylon is thin and layered like a cigar and it crumbles when you press it.
They don't taste the same. Cassia is hot and aggressive and it's what American baked goods are built around. Ceylon is lighter and more floral. A small jar of it costs 3 to 4 times as much per ounce as regular cinnamon, but buy it in a bag and it's about the same price.
McCormick's regular cinnamon is harvested in Indonesia, which makes it cassia. Their gourmet jar is Saigon cinnamon from Vietnam, and that's cassia too.