duplication vs. replication
Duplication is the standard way quantities of 1 - 30,000 CD's or DVD's are produced. The original disc is placed in a reader which then copies the data onto a hard drive. The master is ejected and blank discs are then loaded into the system. Your data is burned (transferred) to the blank discs. The information is verified and the copy then accepted or rejected. Because disc burn speed has increased greatly over the years, it is now possibly to duplicate large quantities of DVD's in a very short time.
Replication is the method used to produce mass quantities (over 30,000) of CD's or DVD's. A "glass master" of your original is made which in turn "stamps" the data onto blank media. The disc is then printed and lacquered for protection. Replication generally takes a much longer time then duplication because of the necessary added steps which can add 7-14 days to complete. Another factor is that a "clean room" environment must be maintained for proper "Mastering". The slightest piece of lint, dirt, etc. can flaw the master, with the defect carried over to the stamped copies.
what is the difference?
There is no difference in the disc's except for a slight compatibility issue between the two processes. A replicated disc will work on all DVD players and computer drives. A duplicated disc will work on players that will read a DVD-R disc. Almost all modern set-top players and computers can play this format. In short, there is VERY LITTLE difference between a duplicated or replicated disc. If you have menus, chapters, alternate sound tracks, extras, etc. on your original, it will be on the the new disc regardless of how it was copied. Most companies are now using duplicated disc's instead of replicated ones because of the cost and time saved by this process and the ever decreasing compatibility issue.