A square kilometer is a unit of area measurement that represents a square with each side measuring one kilometer long. It is commonly used to measure large land areas, such as cities, parks, and countries. One square kilometer is equivalent to 1,000,000 square meters. This measurement is part of the metric system, which is used by most countries around the world. For example, the area of a small city might be expressed in square kilometers to give a clear understanding of its size. Understanding square kilometers helps in planning and development in urban areas and environmental studies.