Answer:

Natural frequency is the rate at which an object vibrates when it is disturbed. ... Natural frequencies are different from forced frequencies, which occur by applying force to an object at a specific rate. When the forced frequency equals the natural frequency, the system is said to experience resonance

Natural Frequency: All physical structures have natural frequencies. These are the frequencies at which the structure will tend to vibrate when subjected to certain external forces. These frequencies are dependent on the way mass and stiffness are distributed within the structure