Also Known As
It is known as Ròu Gùi, 肉桂, in China.
Formerly known as Cinnamomum aromaticum
Chinese Cinnamon's "flavor is less delicate than that of Ceylon Cinnamon," aka True Cinnamon, Cinnamomun verum. It also has a bark which is "thicker, more difficult to crush, and has a rougher texture than that of Ceylon Cinnamon." However, Chinese Cinnamon is the most commonly sold cinnamon spice in the United States, Britain, and India. In India, it is used "both powdered and in whole, or stick form, is used as a flavoring agent for confectionery, desserts, pastries, and meat; it is specified in many curry recipes, where Ceylon Cinnamon is less suitable." It bakes well and is well suited for making cinnamon rolls. It is commercially produced in China and Vietnam. The rare Chinese Cinnamon flowerbuds, known also as Cassia Buds, resemble cloves in commerce. They have a "mild, flowery cinnamon flavor" and are used in India as well as by Romans in ancient times. I came across a beautiful tree in flower at Leu Gardens in Orlando, and that's where I snapped this photo. By the way, my buddy Mycol Stevens has planted and harvested the related Ceylon Cinnamon in Sarasota. He handed me a fresh branch to chew on... mmm, delightful, much like Big Red chewing gum in flavor, but much better of course.
CAUTION: "Due to a blood-thinning component called coumarin, which could damage the liver if taken in huge amounts, European health agencies have warned against consuming high amounts of" Chinese Cinnamon." [4, via 1]
EDIBLE BARK: "The bark of this tree yields an inferior source of cinnamon called Cassia." This is the most commonly used cinnamon in the United States, England, and India.  It is produced commercially in both China and Vietnam.  "Cassia bark (both powdered and in whole, or "stick" form) is used as a flavoring agent for confectionery, desserts, pastries, and meat; it is specified in many curry recipes, where Ceylon cinnamon is less suitable."  It bakes well and is well suited for making cinnamon rolls.
EDIBLE BUDS: "The buds are also used as a spice, especially in India, and were once used by the ancient Romans."  "Cassia buds, although rare, are also occasionally used as a spice. They resemble cloves in appearance and have a mild, flowery cinnamon flavor. Cassia buds are primarily used in old-fashioned pickling recipes, marinades, and teas." [3, via 1]
ESSENTIAL OIL: A golden-colored essential oil is extracted.
MEDICINAL BARK: It is known as Ròu gùi; 肉桂 in China and is one of the 50 fundamental herbs of traditional Chinese medicine (TCM).
- POSSIBLE TREATMENT FOR DEPRESSION AND MENTAL DISORDERS: "Cinnamomum cassia is a medicinal plant that contains a range of bioactive substances, including cinnamic aldehyde. Studies of cinnamic aldehyde treatment in mid-aged rats have resulted in alleviation of chronic unexpected stress-induced depressive-like behaviors. Cinnamic aldehyde is an enzyme inhibitor drug, immunologic drug, and an anti-inflammatory drug. It is administered orally to treat behavioral and mental disorders, targeting the hippocampus and the frontal cortex. Current findings might be beneficial in treating subjects in depression." 
NATIVE TO: Southern China.
- CULTIVATED: It is "widely cultivated there and elsewhere in southern and eastern Asia (India, Indonesia, Laos, Malaysia, Taiwan, Thailand, and Vietnam." 
DESCRIPTION: Evergreen tree.
- HEIGHT: 20-45 feet tall. 
- BARK: Grayish.
- LEAVES: Elongated, hard, reddish when young. 
- HARDINESS: It grows well in central and southern Florida, but severe freezes can damage the tree.
FIVE RELATED SPECIES THAT YIELD CINNAMMON SPICE: "Chinese cassia is a close relative to:
- Ceylon Cinnamon / True Cinnamon (C. verum / aka C. zeylanicum). Sri Lanka produces 80-90 percent of the world's supply. 
- Saigon Cinnamon (C. loureiroi), also known as "Vietnamese cinnamon." It has a higher oil content and thus a stronger flavor. 
- Indonesian Cinnamon (C. burmannii), also called "korintje." Due to disruption of Saigon Cinnamon during the Vietnam War, Indonesian Cinnamon production was increased in both Indonesia and Sumatra.  This species contains the lowest oil content and is thus the cheapest species.  Indonesian Cinnamon is less sweet than Chinese Cinnamon. 
- Malabar Cinnamon (C. citriodorum) from Sri Lanka.
- Indian Cinnamon (C. tamale).
In all five species, the dried bark is used as a spice. Chinese cassia's flavor is less delicate than that of Ceylon Cinnamon. Its bark is thicker, more difficult to crush, and has a rougher texture than that of Ceylon cinnamon." [2, via 1]
 Cassia: A Real Spice or Fake Cinnamon
 "Cassia" - theepicentre.com
 German Christmas Cookies Pose Health Danger, on NPR [via 1]
 Ying, Yao Study published in BIOSIS [via 1]