An airport is a starting point or destination for airplanes to take off and land. According to the CIA world fact book, the United States has over 14,000 airports. The runway(s) may be paved (concrete or asphalt surfaces) or unpaved (grass, earth, sand, or gravel surfaces) but may include closed or abandoned installations. Airports or airfields that are no longer recognizable (overgrown, no facilities, etc.) are not included.
Airport runways are named by number from 1 to 36. The number is based on the direction in which the aircraft take off and land using the compass headings, and then rounded to the closest 10 degrees. Therefore a runway 16 is oriented at 160 degrees or roughly south-west. The opposite end of the runway differs by 18 because it is 180 degrees apart.
Several pieces of airport equipment include RADAR, VORTAC, a navigation system, or Instrument Landing System (ILS), which allow low visibility landings.
Note that not all airports have accommodations for refueling, maintenance, or air traffic control.