1. Action Force: This is the force that one object exerts on another object.

2. Reaction Force: This is the force that the second object exerts back on the first object.

Key Points:

* Newton's Third Law: This law of motion states that for every action, there is an equal and opposite reaction.

* Equal in Magnitude and Opposite in Direction: The action and reaction forces are always equal in magnitude (strength) and opposite in direction.

* Simultaneous: The forces act simultaneously on the two objects.

* Different Objects: The action and reaction forces act on different objects.

Example:

Imagine a book resting on a table.

* Action Force: The book exerts a downward force on the table due to gravity.

* Reaction Force: The table exerts an upward force on the book, preventing it from falling through.

Important Note: Force pairs are not always obvious, and it's crucial to identify the correct objects involved.