Dams: Dams here refer to open land and flat land, and are often called dams in southwest China, such as river dams and flat dams.
Open dam: generally refers to the open space outside the house, such as the square; When it is not rigorous, it is not necessarily flat (as long as it is not a mountain). Sometimes quadrangles and open spaces in residential areas can be said to be surrounded as long as they are open.