An aircraft is able to fly based on the physical law of Bernoulli's Principle. The law stats that the relationship between pressure, fluid flow velocity, and the potential energy of fluids (liquids and gases). The principal states that as the velocity of the fluid increases, the pressure in the fluid decreases. Conversely, as the velocity of the fluid decreases, the pressure in the fluid increases.
This principal is what makes the lift on an airfoil or wing work.
As the wings angle of attack changes, the air above the wing gets disrupted and provides less resistance thus providing lift.
There are four forces at work when an aircraft is in flight. Lift, gravity, thrust and drag. Lift provides the upward acting force. Gravity or weight is the downward acting force. Thrust acts in a forward direction and drag is the backward or retarding force produced by air resistance.
Every aviator knows about the dreaded stall. It's a very basic reaction to the angle of attack being so great, that lift is no longer produced. Many a RC plane owners have become victims of the stall and many aviators have as well.
As long as you don't increase your angle of attack so that you disrupt the flow of air over the wing, you keep on flying. In fact, in a Cessna if your high enough and go into a stall all you need to do is let go of the yoke and the plane with come out of the stall. Of course, if your to close to the ground, your going to drop like a rock.