Trim
Trim tabs are small, secondary flight control surfaces that are attached to the trailing edge of a larger, primary control surface such as an elevator or rudder. The trim tab is used to "trim", or counteract the aerodynamic force on, the control surface and thus stabilize the aircraft in the axis of rotation associated with the primary control. Trim tabs can be either flight adjustable or fixed.
By adjusting the angle of the trim tab relative to the larger control surface, the neutral position of the control surface is changed. This occurs because the distance from the control surface hinge at which the trim tab is mounted provides sufficient moment or force to move the larger surface (SKYbrary).
Aircraft trim holds control surfaces (rudder, elevator, or ailerons) in a specific position, requiring less manual input from the pilot to maintain a desired flight attitude. Trim either moves entire control surfaces (like on a stabilator) or is installed as a separate trim tab (like on an elevator) (Airplane Academy).
Trim Tab. SKYbrary, Retrieved from: https://skybrary.aero/articles/trim-tab.
Aircraft Trim Explained (With Pictures). Airplane Academy, Retrieved from: https://airplaneacademy.com/aircraft-trim-explained-with-pictures/.