In optical disc manufacturing, replication is the process of producing discs via methods that do not involve "burning" blank CD, DVD or other discs; the latter is known as duplication.
The replication of optical discs involves: the creation of a glass master from a client original master. the creation of a nickel stamper from that glass master. the injection molding of clear optical-grade polycarbonate substrates (clear discs) from that stamper. the metallizing and lacquering of those substrates to produce compact discs and DVDs.
References Bennett, Hugh. " The Demise of Low-Run CD Replication." EMedia Professional Aug 1999. How compact discs are made -- Explained by a layman for the laymen Kevin McCormick