What does squeaky floor repair actually involve?

It involves finding the exact connection that is moving and closing it. In most houses that means a subfloor panel or plank has separated slightly from the joist beneath it, so we locate that spot, work out whether we can reach it from below, and draw the subfloor back down tight to the joist. On stairs it means refastening or re-wedging the specific tread joint that has loosened. What it does not involve is sanding, refinishing, or replacing flooring.