Draw an aerofoil cross section, inclined with the leading edge higher than the trailing edge. Draw a horizontal longish arrow point towards & touching the trailing edge of the aerofoil.
This represents the relative airflow towards aerofoil, giving an AoA with no vertical movement.
Now add a small downwards pointing arrow that touches the tail of the horizontal arrow. These are the components of the airflow the aerofoil will experience if it moves up while moving forward ie a relative airflow from the front and a relative airflow from above.
The combined effect of those airflow components is the vector sum of them - and that's what the aerofoil experiences. Draw an arrow from the tail of the small, vertical arrow to the head of the long horizontal arrow. Compare the AoA now to the original.