Let’s backtrack a little bit. While in flight, planes experience four types of forces: lift, gravitational (opposing lift), thrust, and drag (opposing thrust). Air passing over the airplane travels in the direction of the drag forces (planes experience multiple types of drag). The wing is designed to create a pressure difference with higher pressure below the wing and lower pressure above, producing lift. In addition, the air that passes over and under the wing is often deflected downward upon leaving the wing’s surface, contributing to the lift force.
In level flight, the plane flies parallel to the ground, and to the oncoming air. When the plane’s nose aims upward so that the plane can climb, the angle of attack (in this case also called the climb angle) increases. Once the critical angle is surpassed, flow over the wing breaks down and lift is lost. It is necessary to push the plane into a descent in order to regain lift. After entering the descent, the pilot can ease the plane back to level flight with lift restored.
Aerobatics planes enter stalls purposefully for maneuvers such as spins. In a fully developed spin, the inside wing experiences more drag and less lift and is considered “fully stalled,” while the outside wing experiences more lift and less drag, making it “not as stalled.” Completing a spin is basically the same idea as recovering from a stall— the nose must be pitched forward with both ailerons neutral (flat). Opposite rudder is applied to help correct from the direction of the spin (if leaving a counterclockwise spin, apply right rudder). Pilots often decrease the airspeed in a stall recovery to avoid putting excess stress on the plane.