A kite is an aircraft consisting of wings tethered to an anchor system. Frequently a wing of a kite is referenced as "kite". The necessary lift that sustains the kite in flight is generated when air flows above the kite's surface, producing low pressure above and high pressure below the wings. The interaction with the wind also generates horizontal drag along the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of one or more of the lines or tethers to which the kite is attached. The anchor point of the kite line may be static or moving (e.g., the towing of a kite by a running person, boat, free-falling anchors as in paragliders and fugitive parakites or vehicle). The same principles can be used in water and experiments have also been made with lighter-than-air kites (kytoons) Kites may be flown for recreation, art or other practical uses. Sport kites can be flown in aerial ballet, sometimes as part of a competition.