The backing is the lattice webbing on the back of the carpet that holds the carpet fibers together.
If dirt is transferred out from the rug for the cloth, you'll need to use a rug cleaner product areas available at any shop. In as young as 72 hours mold can start growing on that wet dry walls. http://delenadiaries.com/go?a:aHR0cHM6Ly93d3cuaGFwcHlsaXZlbGlmZS5jb20vc2hhcmUvP3VybD13d3cuZGFtc2tpZS5wbC8yMDEyLzA1LzA5LyZ0aXRsZT0lRTclQkIlOEYlRTUlOEUlODYlRTglODclQjMlRTYlODglOTAlRTklOTUlQkYlRUYlQkMlOEQlRUYlQkMlOEQlRTclODglQjElRTclOTQlOUYlRTYlQjQlQkIlRUYlQkMlOEMlRTclQkUlOEUlRTUlQTUlQkQlRTclOTQlOUYlRTYlQjQlQkIlRUYlQkMlOEMlRTUlQjAlQjElRTUlOUMlQTglRTclOUMlQkMlRTUlODklOEQlRUYlQkMlOEQlRUYlQkMlOEQlRTUlQkYlQUIlRTQlQjklOTAlRTclOTQlOUYlRTYlQjQlQkIlRUYlQkMlOEMlRTQlQkIlOEUlRTglQkYlOTklRTklODclOEMlRTUlQkMlOD