How does Newton’s third law explain action and reaction?

In his Principia, Isaac Newton established that for every action, there is an equal and opposite reaction. This means that when two bodies interact, they exert forces on each other that are equal in magnitude and directed in opposite directions.12

A critical aspect of this law is that the action and reaction forces always act on different bodies, never the same one. Because these forces are applied to separate objects, they do not produce a net force on the two-body system as a whole.1

For example, when an object rests on a table, the object exerts a downward force on the table, while the table exerts an equal and opposite upward force on the object. These two forces constitute an action-reaction pair. It is important to distinguish these from forces acting on a single body, such as the table's upward force and the downward force of gravity acting on the object; these two forces balance each other to create equilibrium, but they are not an action-reaction pair under the third law.1