Newton's third law states that every action has an equal and opposite reaction. This can be understood with examples. If you hit a nail with a hammer, the nail goes deeper into the wood due to the action force. Consequently, the force due to the nail pushes the hammer backward. Consider a man sitting on a recliner. A force due to gravity acts on him. The recliner exerts an equal and opposite normal force that keeps him stationary. However, this is not an "action-reaction" pair as the forces are acting on the same body. The force of gravity exerted by the man on Earth is the reaction pair to Earth's pull on him. Also, in reaction to the normal force by the recliner, the man exerts an equal force on the recliner. Therefore, not only contact forces but non-contact forces, such as the force due to gravity, also obey Newton's third law.