To understand how an aerofoil creates lift you have to appreciate the way that air flows around the wing. The air separates at the leading edge, with air flowing over the top surface speeding up and air flowing below the aerofoil slowing down.
You can see this effect in the diagram where the coloured bands represent air molecules that were initially in the same relative vertical position. Increasing the angle of attack makes the air flow even faster over the top surface, and creates more lift. But if the angle is increased too much then the air stops flowing smoothly over the aerofoil and becomes turbulent.
In the next section you will see how the air flow around the aerofoil creates forces on the wing and find out more about what happens in a stall