A propeller can be seen as a rotating fin in water or a wing in air. The horizontal axis of rotation produces a dynamic force as thrust. The force produced is from the difference in pressure from the forward and rear surfaces of the blades.
On an aircraft, the propeller is an airfoil, much like the wing of an aircraft, except that the shape of the airfoil varies continuously throughout the length of the blade. The tip of the propeller often operates at or near the speed of sound, causing a raucous noise.