Landing is the last part of a flight; where a spacecraft or aircraft returns to the ground. Hitting the ground too hard is prevented by wings (including rotor wings), a parachute or rockets or a vertically directed engine. Aircraft usually land at an airport on a runway or helicopter landing pad.
For aircraft , landing is generally accomplished by trading airspeed for lift. The first phase is the flare, where the rate of descent will be reduced by transitioning to a stall attitude. After slowing down, the plane changes pitch into the landing attitude shortly before touching down.
In a perfect touchdown, assuming there is no crosswind, contact with the ground is made just as the forward speed is reduced to the point where there is no longer sufficient lift to remain aloft. If there is a crosswind, techniques such as a crab landing or a slip landing are used to land the plane safely.