This concept is described by Newton's Third Law of Motion, which states:

* For every action, there is an equal and opposite reaction.

This means that whenever one object exerts a force on another object (action), the second object exerts an equal and opposite force back on the first object (reaction).

Here are some examples:

* Walking: When you push your foot against the ground (action), the ground pushes back on your foot with an equal and opposite force (reaction), allowing you to move forward.

* Jumping: When you jump up, you exert a force downward on the ground (action). The ground exerts an equal and opposite force upward on you (reaction), propelling you into the air.

* Rocket launch: When a rocket expels hot gases downward (action), the gases exert an equal and opposite force upward on the rocket (reaction), causing it to launch.

Understanding this concept is crucial in various fields, including physics, engineering, and aerospace.