Refer to figure.
The angle of attack (a) is the angle between the chord line of an airfoil (or wing) and the direction of the oncoming airflow. It's a critical aerodynamic parameter that directly influences the lift and drag forces acting on the airfoil. Increasing the angle of attack generally increases lift up to a certain point, beyond which lift may decrease due to flow separation and stall. Controlling the angle of attack is essential for pilots to maintain stable flight and avoid stalling conditions.