A wing is part of an animal that allows it to fly. Birds have wings, and so do butterflies and many other insects. By moving its wings, the animal can produce lift and get off the ground.
Airplanes also have wings. Those wings cannot be moved, they are stable, but the wings also produce lift, so the airplane will get off the ground if you move it fast enough.
People also talk about wings of buildings. What they mean is usually a part of the building that is separated from the rest (for example: the west wing of a building).