harmonics and fundamental freuency

[Bhuvanesh123]

i need explaination other that guitar string examples(related to electronics).what is harmonics and fundamental frequency. when and where harmonics occurs .thank you in advance

 

[cl10greg]

Quick run down and link.

The fundamental frequency is the lowest frequency of a periodic wave (it is also the first harmonic).
Harmonics are multiples of the fundamental frequency. They are equally spaced by the fundamental frequency.

https://www.physicsclassroom.com/class/sound/Lesson-4/Fundamental-Frequency-and-Harmonics

 

[Bhuvanesh123]

to make sqaure wave we only taking odd hormonics of high frequency sine wave.why/