A replica or copy of something is a duplication, and the process of making it is also duplication. Duplication of important computer files is always a good idea — that way you have a backup if you accidentally delete something or your laptop malfunctions.
The earliest meaning of duplication was "act of doubling," from the Latin duplicare, "to double." By the 1580s, it gained the sense of "an act of making or repeating something essentially the same." Duplication can be as simple as making paper copies (or duplicates) with a Xerox machine, or as complicated as certain genetic processes in which parts of DNA are repeated.