Commonly known as the "tail section," the empennage includes the entire tail group consisting of fixed surfaces such as the vertical fin or stabilizer and the horizontal stabilizer; the movable surfaces including the rudder and rudder trim tabs, as well as the elevator and elevator trim tabs. These movable surfaces are used by the pilot to control the horizontal rotation (yaw) and the vertical rotation (pitch) of the airplane.
In some airplanes the entire horizontal surface of the empennage can be adjusted from the cockpit as a complete unit for the purpose of controlling the pitch attitude or trim of the airplane. Such designs are usually referred to as stabilators, flying tails, or slab tails.
The empennage, then, provides the airplane with directional and longitudinal balance (stability) as well as a means for the pilot to control and maneuver the airplane. This is further explained in subsequent chapters.