Angle of attack is like how you hold a toy plane in the air to make it fly. You know that if you hold it level, it will just drop to the ground. But if you hold it up at an angle, it will soar up into the air!
Now, just like a toy plane, real planes also need to be held at an angle to fly. This angle is called "angle of attack".
When a plane takes off, it needs to point the nose up slightly to get enough lift from the wings to get off the ground. Once it is in the air, the pilot can adjust the angle of attack to make the plane climb, descend or fly straight.
The angle of attack also affects how much air flows over the wings. If the angle is too high, the air flow can become disrupted and the wings might not produce enough lift. This is called a "stall" and can cause the plane to drop suddenly.
So, to sum it up, angle of attack is the angle at which a plane's wings need to be to stay in the air, climb or descend, and avoid a stall.