Optical Disc Systems such as Dvds and Cds store data optically they use laser beams. Like Magnetic disks Optical Disks are divided into tracks and sectors but use a single grooved spiral track. Optical disks gave a high capacity of at least 650MB.
Burning is a process of recording data onto an optical disc.
Spots on the disc are used to represent data's the unchanged areas on the disc are called lands. The transition between a pit and a land represents a 1 no transition represents a 0.
Pits can be molded into the disc surface or they can be created by changing the reflectivity of the disc.
The difference between magnetic disks and optical discs is that with magnetic discs such as floppy discks data is stored magnetically the data is represented using magnetis allignments. Optical discs store data using laser beams.