What is the difference between Angle of Incidence (AoI) and Angle of Attack (AoA)?
Angle of Incidence is fixed by the designer of the aircraft. It does not change in flight.

Angle of Attack is the angle between the chordline of the wing and relative airflow during flight.



That is definitely something that changes during operation of the aircraft in flight. Consider slow flight, for example. You reduce power and raise the nose to reduce airspeed. The direction of the airflow remains the same, but the angle between the airflow and the wing chordline, the Angle of Attack, increases. Raise the nose too much (and hence increase the AoA), and the airflow will separate from the top of the wing and you will stall.

On aircraft like Cessna trainers, the stall warning is a very basic indicator of Angle of Attack, to warn you when you are about to stall.



More advanced Angle of Attack indicator systems use a vane to measure the angle of the relative airflow, and give you more information about AoA.