Gliding is when an object or animal goes through the air without active flight. All gliders use an aerofoil to slow their rate of descent. Glider planes have wings, and gliding animals have membranes which they stretch out. By using rising air they can prolong their stay in the air. The word 'soaring' describes this, and is also used for the sport of gliding.
Air will rise if it is heated by the ground or if it is deflected by mountains. Improvements in aerodynamics, in instruments and in the understanding of the weather have allowed flights over great distances at high speeds. The world record distance is now over 3000 km.