Harmonic oscillator is a physical system that, when displaced from its equilibrium position, experiences a restoring force that is directly proportional to the displacement. This proportional relationship is a key characteristic, and the restoring force always acts in a direction to bring the system back to its equilibrium. An example is a mass attached to a spring. If you pull or push the mass, the spring exerts a force to return it to its resting position. The restoring force follows Hooke's Law. This results in an oscillation, or back-and-forth motion, that can be described mathematically using sinusoidal functions like sine or cosine waves. The motion is often referred to as simple harmonic motion (SHM) if there are no other forces like damping (friction) or external driving forces.
