"Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first."
Newton's third law can be also known as the 'action-reaction' law. This is because Newton's law states that when one forces acts on an object, the other object will apply an equal and opposite force. The only way to make an object move is to apply a greater force an object. All forces act in pairs. For instance, a stationary object on a table is being pulled down to earth by gravity, while at the same time, the table is pushing up with lift with equal force to make a net force of 0N.
This picture shows that the person is applying 100N to the wall, and the wall is applying the same force back to make it stay idle. The purpose of the third law is to explain why objects can move by a force. Every object in the universe that begins moving or is in motion is opposed by another force in the other direction. Even when there is not any movement, forces are being exerted in pairs. This is seen when a person sits in a chair. Most people only recognize the force of your body weight pushing down on the chair, but there is also the reaction of the chair pushing up against your mass.
A real life example of this is when a rocket ship launches into space. The aircraft is elevating upwards toward the sky due to the fact that the gases are equally pushing back down towards the ground, allowing the rocket to accelerate. This other force interacts with the rocket ship's motion as it occurs in the different direction. Forces can act in pair yet be unbalanced, too. Multiple forces exerted on something can work in opposite directions but create a net force not equal to 0N. This causes a change in the object's motion.