Also known as PVD, an advanced method of creating a final finish compared to electroplating or polishing.  The PVD process actually changes the molecular structure of the surface and several millimeters into the substrate of a metal object such as a faucet. The result is a change of the reflective properties of the metal object.  The depth of the change is dependant upon many variables established by the operator.  If an item is scratched it does not matter as the substrate is the same color as compared to a thin layer of plating or polishing.  For more detail, please read this report.