In car terminology, a wing is like a spoiler, only bigger. The purpose of a wing is to provide downforce, which makes the car stick to the road better at high speed. Wings are not at all necessary for normal street or highway driving, and in fact most cars with wings (usually riceboys) look garish and cheap.

stupot sez: A wing (in the UK at least) is also the part of the car above the front wheel. From the front door to the headlight, wheel arch to hood. That's a wing.