As the wing moves through the air, the airfoil is inclined to the flight direction at an angle. The angle between the chord line and the flight direction is called the angle of attack.
Angle of attack has a large effect on the lift generated by a wing.
When an airplane takes off, the pilot applies as much thrust as possible to make the airplane roll along the runway. The nose of the airplane rises, increasing the angle of attack and producing the increased lift needed for takeoff. The magnitude of the lift generated by an object depends on the shape of the object and how it moves through the air. For higher inclinations, however, the dependence is quite complex. As an object moves through the air, air molecules stick to the surface.