Leonardo da Vinci’s ornithopter was a flying-machine concept with wings intended to flap like those of a bird.
Leonardo studied birds extensively because he believed their flight could reveal principles useful to human aviation. His notebooks contain drawings of wing structures, human-powered machines, and mechanisms intended to convert the movement of a pilot into wing motion. The ornithopter concept reflects that early focus on imitation of living flight.
Leonardo did not build a successful human-powered ornithopter. Human muscles cannot provide the sustained power needed for a large flapping aircraft with the materials and mechanisms available in his period. Later aviation succeeded with fixed wings and engines rather than birdlike flapping.
An ornithopter is not the same as a glider. A glider has fixed wings and remains airborne by using aerodynamic lift while descending or riding rising air. The term “ornithopter” specifically refers to flight produced by flapping wings.