Simulacrum
The concept of copies of something for which there is no original. Basically, copies of things that never existed. This concept usually deals with ideology as opposed to a physical "original" for which something can be copied.
A perfect example would be a 50s diner. They are all over, yet no diner in the 50s was anything like these commercial restaurants. The 50s diner is essentially the phsyical embodyment of the IDEA of the 50s as opposed to things that truly existed in the decade. This concept has been copied over the years, and now 50s diners are just about everywhere. 

In a more recent example, simulacrum can be found in today's music. The genre of "new-new wave" has spread like a virus thanks to bands like The Killers and The Bravery. But if you go back and listen - it sounds nothing like new wave. Someone decided to call it new wave thanks to something like the use of synths and warbly guitar solos. Other bands then copied this style, and what you have are copies of copies of things that never really happened. Copies of "new wave" that doesn't really sounda thing like real, genuine new wave.