When a material oscillates at a high amplitude at a specific frequency, this is referred to as resonance.
The phenomenon of resonance frequency occurs when an external force or a vibrating system forces another system around it to vibrate with greater amplitude at a specified frequency of operation.
The best examples of resonance can be found in a variety of musical instruments all around us.
When someone hits, strikes, strums, drums, or tweaks a musical instrument, it causes the instrument to oscillate or vibrate at its natural frequency of vibration.