Natural frequency is the rate at which a system oscillates when it is disturbed from its equilibrium position and then allowed to move freely. Every physical system, such as a swing, guitar string, or building, has its own unique natural frequency determined by its mass and stiffness. When a system is excited at its natural frequency, it can resonate, leading to larger amplitude oscillations. This phenomenon is important in various fields, including engineering and music, as it can affect the stability of structures and the quality of sound produced by instruments.