Vibration, standing waves in a string. The fundamental and the first 5 overtones in the harmonic series.
A vibration in a string is a wave. Resonance causes a vibrating string to produce a sound with a constant frequency, i.e. constant pitch. If the length or tension of the string is correctly adjusted, the sound produced is a musical tone. Vibrating strings are the basis of string instruments such as guitars, cellos, and pianos.