The chair has a back, but the stool doesn't.

A chair is a seat with a back.

Among the seats, Mazar was the earliest one. It is the predecessor of the stool. Adding a backrest to the stool turns it into a chair. Stool is called "stool" in the folk. It was originally used when stepping on the horse and sedan chair, so it is also called horse stool and sedan chair. Among the folk names, there is also the "martial stool", which is named because people who practice martial arts sit like clocks and don't need to rely on anything. Stools have simple materials and a wide range of uses, so they are more popular than chairs. The shapes of stools are very rich. In the early stage, they were rectangular, which lasted until the Ming Dynasty. In the Qing Dynasty, they became square, and there are also circular, fan-shaped, plum blossom shaped, hexagonal and so on.