What is Optical disc?

In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc that encodes binary data in the form of pits and lands on a special material, often aluminum, on one of its flat surfaces. Its main uses are physical offline data distribution and long-term archival. Changes from pit to land or from land to pit correspond to a binary value of 1; while no change, regardless of whether in a land or a pit area, corresponds to a binary value of 0.

Non-circular optical discs exist for fashion purposes; see Shaped compact disc.