A jet engine operates on the principle that the force of the gases that rush out the back of the engine are equal to the force of the jet accelerating forward. When a missile is launched from the ground, the rocket engines fire hot gases downward. This is the action. The upward motion of the missile away from the sudden thrust of the gases is the reaction.

If you are trying to skateboard, there is no way you can give yourself forward movement (the reaction) unless you push off the ground with your foot (action). If you are trying to push a heavy box across a floor, you can feel that reaction as the box pushes against you. There is also a static friction force involved (between your feet and the floor) that allows the box to move forward without you moving back. Imagine trying to push the box with inline skates on your feet. The box would cause your feet to roll back (reaction) with the same force that you are pushing with (action)!