According to the International Civil Aviation Organization (ICAO) a runway is a "defined rectangular area on a land aerodrome prepared for the landing and takeoff of aircraft". Runways may be a man-made surface (often asphalt, concrete, or a mixture of both) or a natural surface (grass, dirt, gravel, ice, or salt).
Read more about Runway: Orientation and Dimensions, Placement and Grouping, Declared Distances, Sections of A Runway, Runway Markings, Runway Safety, Pavement, Active Runway, Runway Length