The Angle of Attack is the angle at which relative wind meets an Aerofoil. It is the angle formed by the Chord of the aerofoil and the direction of the relative wind or the vector representing the relative motion between the airplane and the weather. The angle of attack can be simply described as the distinction between where a wing is pointing and where it is going.
The angle of attack is the angle at which the oncoming air meets the wing. Normally, the greater the angle of attack, the more lift is produced by the wing. However, this is only true to a point. At some factor, the wing reaches its crucial angle of attack, and at greater angles of attack, the quantity of lift produced drops considerably.
The amount of lift produced by a wing is proportional to the angle of attack, with greater angles generating more lift. This continues true up to the stall point, where lift starts to decrease again. Aircraft travelling at high angles of attack can suddenly cross the stall point if a powerful wind changes the obvious wind direction, an impact that is seen mainly in a low-speed airplane. The aircraft continues to be flyable when moving at right angles to the direction of motion.