Geographers use the term "area" to refer to any particular portion of Earth's surface. It may be as small as a park or a neighborhood, or as large as a continent or an ocean. Metropolitan areas, for example, help define the borders of large population centers for a census and other official purposes. The metropolitan area of Tokyo, Japan, contains many cities and over 35 million people.

Area is also an exact measure of the size of a surface with specific boundaries. For example, the U.S. state of California has a land area of 403,932 square kilometers (155,959 square miles).

For maps, it's important to represent area accurately so the sizes of different regions can be compared properly. The surface of a sphere such as Earth can never be perfectly reproduced on a flat map. As a result, mapmakers, or cartographers, use different types of distortions, or projections, depending on which features they want to show most accurately. A Mercator projection distorts area but preserves accurate directions; the Mollweide projection shows area accurately but tends to distort directions and shapes.