An airfoil is a shape that produces forces when moved through a fluid (i.e. air). Airfoils are easily seen in aircraft wings, propeller blades, and even household fans. A Frisbee functions as an airfoil as well, and can sustain flight because of this property.

The primary idea behind an airfoil is that sections of the air like to stay together. When the blade cuts through the air, the air on top moves faster, since it has to travel a farther distance around the airfoil, while the air on the bottom is relatively unimpeded.

Bernoulli's Principle is a fun law that states that the faster a fluid travels, the less pressure or potential energy it has. Since the air on top travels faster, it creates a low-pressure zone directly above the wing. The higher pressure below the wing then pushes the wing upwards, creating a force called Lift.

At the same time, the airfoil is traveling at a high enough speed that air resistance becomes a major factor, and a Drag force is created in the direction opposite to motion.