The short answer - duplication for short runs up to 500 copies, replication for larger jobs.

The longer answer - The process of duplication is perfect for low quantity copy jobs. Blank recordable media is used - you may know them as DVD-R. Data from your master disc is then copied onto the playing side of the disc by burning a series of dots and dashes into a photosensitive layer.

When this duplicate of your master disc is then played, it translates the dots and dashes back into the original data from your master.

Replication is a cost-effective process if you need a larger number of copies. Your master disc is used to create a glass master, which acts as a kind of stamp. The glass master is then 'pressed', like a pastry cutter. The data is perfectly replicated by a series of pits and lans on the shiny playing side of the disc.