In Newton's third law, every "action" has an equal and opposite what?

Newton’s Third Law: Action & Reaction. Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. His third law states that for every action (force) in nature there is an equal and opposite reaction. If object A exerts a force on object B, object B also exerts an equal and opposite force on object A. In other words, forces result from interactions. Examples of action and reaction involving aerodynamics: The motion of lift from an airfoil, the air is deflected downward by the airfoil’s action, and in reaction, the wing is pushed upward. The motion of a spinning ball, the air is deflected to one side, and the ball reacts by moving in the opposite direction. The motion of a jet engine produces thrust and hot exhaust gases flow out the back of the engine, and a thrusting force is produced in the opposite direction.

Source: NASA