Newton's Third Law of Motion: For every action, there is an equal and opposite reaction.
Bernoulli's Principle: an increase in the speed of moving air or a flowing fluid is accompanied by a decrease in the air or fluid's pressure.
In order for an airplane's wings to overcome the force of gravity they must produce lift. Both Newton's Third Law of Motion and Bernoulli's Principle are needed to understand lift. As the wing of an airplane meets the oncoming air, the air is pushed downward under the wing. The wing has an equal an opposite reaction and is forced upward. As the air travels over the curved upper surface of the wing, it has to travel faster than the air passing under the lower surface of the wing. If the air above the wing is moving faster than the air below the wing, it is exerting less pressure on the upper surface of the wing. The increased pressure on the lower surface of the wing moves the wing upward. This is how the wings of an airplane produce lift.
The shape of the wing, with its curved upper surface, is called an airfoil. A propeller has a similar shape. When the prop is spinning, it is causing a similar force because of its shape and angle as it meets the oncoming air. The force that is applied by the prop is call thrust. The resistance of the airplane and all its parts to the forward motion caused by the prop is called drag. The more things on an aircraft that disrupt the airflow (extended landing gear or extended flaps) the more drag is produced, slowing the airplane.