Newton's 3rd Law
When one body exerts a force on a second body.
law:
When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.
One example of action/reaction force is a person pushing against a wall, another example is someone dribbiling a basketball, my last example is a baseball player at bat swinging the bat and hitting the ball.