How do you use optical disc?

An optical disc has one long spiral track of data. Along the track there are areas that are reflective and areas that are not. A laser is shone along the track, the reflective areas are read as binary 1's while the non-reflective areas are read as binary 0's. CD-R's and DVD-R's have a dye layer that is used to write your own CDs and DVDs with the appropriate hardware.