Stabilator

[2] Because it involves a moving balanced surface, a stabilator can allow the pilot to generate a given pitching moment with a lower control force.

This is the point at which the pitching moment is constant regardless of the angle of attack, and thus any movement of the stabilator can be made without added pilot effort.

Stabilators were developed to achieve adequate pitch control in supersonic flight, and are almost universal on modern military combat aircraft.

[6] Entering service in 1951, the Boeing B-47 Stratojet was the world's first purposely built jet bomber to include one piece stabilator design.

For example, the North American F-100 Super Sabre, used gearing and a variable stiffness spring attached to the control stick to provide an acceptable resistance to pilot input.

[8] In modern fighters, control inputs are processed by computers ("fly by wire"), and there is no direct connection between the pilot's stick and the stabilator.

The movable horizontal stabilizer is adjusted to keep the pitch axis in trim during flight as the speed changes, or as fuel is burned and the center of gravity moves.

Grumman F-14 Tomcat jet fighter during a takeoff, with stabilators deflected upwards
Piper Cherokee with stabilator (and anti-servo tab) deflected upwards
In transonic flight shock waves form on the upper surface of the wing at a different point from the lower surface. As speed increases, the shock wave moves backwards over the wing. On conventional tails this high pressure causes the elevator to be deflected downwards.
Adjustable stabilizer on an Embraer E170 , with markings showing the degree of nose-up and nose-down trim available