The pitcher's mound in baseball is a raised area of dirt in the center of the infield containing the pitcher's rubber, from which a pitcher throws. It is called a mound because it is slightly sloped, like a small hill.
The height of the mound corresponds to the distance between the bases; for every 10 ft that distance goes down, the pitcher's mound must go down two inches. A diamond with bases that are 90 ft apart has a 10-inch mound, one with 80 ft apart has an 8-inch mound and so on. On top of the mound, there is a flat piece of rubber. The rubber itself is 24 inches long and is about 60 feet away from home plate (for a 90 ft field).