A margin runs around your yard. It's called your property line. Here at my house the garbage truck just came by. It grabbed the big plastic tub and emptied it. Life along the margins.
Power lines come in along the back margin.
Water and gas lines come in along the front margin. The sewer line goes out. Life is flowing to, through, and from the margins. Your house itself has an outer wall. From an airplane, the only way you can see there is life in a house is when it enters or exits.