DVDs are made in different ways depending on the amount of information that is recorded on the disc. DVDs may be single or double layered and single or double layered double sided.
Single Layer DVDs (DVD-5 - 4.7GB)
These DVDs are made the same way as a CD with one additional polycarbonate layer added between the label and the pits and lands.
Double Layered DVDs (DVD-9 - 8.5GB)
Double layered DVDs have a semi reflective layer and a reflective layer giving two layers to store information.
Double Sided DVDs (DVD-10 - 9.4GB)
Double sided DVDs consist of two discs bonded back to back with the reflective layers in the middle and both sides are repairable. Double sided DVDs use a different size of micro-abrasive polishing papers to prevent the manufacturer’s label area from being removed during the repair process.
Double Sided/Double Layered DVDs (DVD-18 - 17.1GB)
Double sided/double layered DVDs are simply two double layered discs bonded back to back.