What is angle of attack and how does it affect lift?

Angle of attack (AOA) is the angle between the wing's chord line and the relative wind direction. As AOA increases, lift coefficient increases nearly linearly up to a critical angle (typically 14-18 degrees for most airfoils). Beyond this critical angle, the airflow separates from the upper surface causing stall, where lift decreases dramatically. AOA is a primary control parameter for adjusting lift during flight.