biquad to filter out unwanted signal ?

I have seen some people use biquad object at the audio input to filter out unwanted noises or frequency to avoid mistakes for pitch tracking. However, I never understand how they know those parameters for biquad.

Is it a try-and-error thing? Are there some good tutorials I should study first before I can figure out the parameters for biquad~ to help improve the precision of pitch tracking ?

Take the example of using biquad for better pitch tracking result. What is the usual process of finding the biquad parameters ?

Please share your experiences.

Thanks.