From SKYbrary Wiki
A stabilator, sometimes referred to as an all-moving tail, is a fully movable aircraft horizontal stabilizer. In this type of installation, the entire horizontal tail surface is responsive to pilot control wheel or control stick inputs. This is in contrast to the more common elevator control movement associated with both a fixed or a trimmable horizontal stabilizer. Stabilators are most commonly found on high speed military combat aircraft where they are used to enhance manoeuvrability and to eliminate the mach tuck caused by shock wave formation behind the elevator hinge line of a conventional tail. Stabilators are also installed in some light, general aviation aircraft.
Stabilators are designed to pivot about their aerodynamic center and, as a consequence, very little pilot effort is required to make a control input. This amount of effort does not vary with airspeed or angle of attack. To prevent over-controlling, the stabilator on a light aircraft is fitted with an anti-servo tab on its trailing edge. Control input causes the anti-servo tab to deflect in the same direction as, but further than the stabilator. This additional deflection induces an aerodynamic force which resists the pilot input. In most cases, the anti-servo tab also acts as a trim tab.
Supersonic aircraft are not fitted with anti-servo tabs. In older aircraft, the potential for over-controlling due to light control forces was addressed by resistance force generated by springs or hydraulic pressure. In modern military jets, fly-by-wire controls moderate the control inputs to prevent over-controlling.