Hearing aid feedback is one of the major problems hearing aid users face. It is the whistling or squealing noise that occurs in hearing aids when the sound from the hearing aid speakers (receiver) loops back around into the microphone.
Feedback in a hearing aid can occur for many reasons. Hearing aid manufacturers have come a long way in recent years to reduce the likelihood of feedback in a hearing aid.
To read more information on hearing aid feedback, check out this article.