Here's a breakdown:

* Normal Force: This is the force exerted by a surface perpendicular to the surface of contact. It's a reaction force that prevents an object from passing through the surface.

* Example: Imagine a book resting on a table. The book exerts a force (due to gravity) on the table. In response, the table exerts an equal and opposite force on the book, pushing it upwards. This upward force is the normal force.

* Key Points:

* The normal force is always perpendicular to the surface.

* It's a contact force, meaning it only exists when two objects are touching.

* The normal force is often equal in magnitude but opposite in direction to the force of gravity acting on an object at rest on a horizontal surface.

Let me know if you'd like to explore any of these concepts further!