This phenomenon is known as acoustic feedback and it occurs when sound that comes from a pair of speakers creates a loop that circulates back and forth between the speakers and your microphone.
For example you’re in a meeting, enjoying your chat, and suddenly you hear a noise that almost shreds your eardrums. Despite Zoom’s uncanny ability to provide you with an excellent video meeting every single time you use it, with any technology, there’s bound to be some problem every once in awhile.