So as the air hits the lower surface of a wing, it pushes the wing up. Now blow as the air hits the paper it pushes it up. This is impact at work. One of the major misconceptions is that this is what lifts airplanes up. This is plays a factor, however the major factor is Dynamic lift.
Dynamic lift is a little more involved to describe.
Let's start with that same piece of paper. Turn the top of the paper so that it makes a slight curve shape. Blow on top side of the curve. Since the air on top of the piece of is traveling faster than the air below the piece of paper, this creates a low pressure, lifting the piece of paper up. This Principle was discovered by Daniel Bernoulli, a Swiss physicist.