A baseball park, baseball stadium, or ball park / ballpark is a place where baseball is played. It refers to the field of play, seating areas (if any) and any other things added to it.
The flexible rules about baseball fields (aside from the rigid rules of sizes of basepaths and pitcher's mound) allow ballparks to have their own character and quirks. This happens at all levels of baseball, amateur and especially professional. This makes each stadium interesting and unique.
The infield is a square (usually called a "diamond"), with each side being 90 feet (27 m) long. In each corner of the square, there is a "base", which is a square with sides of 15 inches (38 cm). One of the bases is called home base or home plate, and the sides of the square that touch home plate are extended beyond the two nearest bases until the outfield fence (which is 300 feet (91 m) or more away from home plate) to form the foul lines. Most of what happens in a baseball game happens in the area of the field in between the foul lines and the outfield fence, which is called fair territory. All other areas of the field (except the foul lines) are called foul territory.
↑http://web.mit.edu/~xsdg/Public/papers/himcm-2003.pdf "The width is the distance between foul poles... the Twins’ field width (473.9 ft) and the Braves’ field width (470.2 ft) is not significant. However, the difference between the Rockies’ and Yankees’ field widths (492.9 ft and 446.9 ft, respectively) is very significant."