Technically the ground is not attached to one side. That would violate any of the more competent building codes that govern >90% of the USA. There is an insulated hot wire (usu. black) and an insulated neutral wire (usu. white), both go all the way to the main panel. A third [ground] wire (green, or bare copper) grounds junction boxes, receptacles, etc. and the ground plug on three-prong receptacles. The ground circuit literally is attached to ground, via a cold water pipe and/or a brass rod pounded into the earth.