Because these three are made in much the same way, they are put together.
The history of steamed buns, buns and rolls can be traced back to the Spring and Autumn Period and the Warring States Period, and the Romance of the Three Kingdoms has an account of Zhuge Liang sacrificing steamed buns to the god of Lushui.
The flour mixed with water, sugar, etc., fermented and steamed into the food, the finished product in the shape of a hemisphere or a long strip known as the steamed buns, in the production of meat, vegetables, soybean paste and other fillings into the buns, plus salt, sesame sauce, green onion oil, etc., pinched into a pleated is the rolls.