Four Forces & Bernoulli's Principles

Drag: The air resistance that tends to slow the forward movement of an airplane.
Weight: A force that acts on the plane to pull it back to earth.
Lift: The upward force that is created by the movement of air above and below a wing. Air flows faster above the wing and slower below the wing, creating a difference in pressure that tends to keep an airplane flying.
Thrust: The force that moves a plane forward through the air. Thrust is created by a propeller or a jet engine.

Bernoulli's Principle: an increase in the speed of a fluid produces a decrease in pressure and a decrease in speed produces an increase in pressure

The curved top of a wing creates a longer distance from front to back than the straight bottom. This causes the air on top to travel farther, and thus faster, to reach the back than the air underneath, creating a difference in pressure between the two surfaces