How Optical Disks Work?

We are all living in a generation where even optical disks are becoming obsolete. They are being replaced by magnetic discs and solid state discs. The even more compact pendrives are much more preferred than this optical disks.
But, even so, how many of are aware of how these Compact Discs (CDs) , or Digital Versatile Discs (DVDs)  or Blu-Ray Discs actually work?

Here, I'll explain in a simply way as to how these devices are used to store and read data.

As one might know, all digital data, fundamentally consists of 0s and 1s. These in any electrical devices are identified in terms of voltages, the higher voltage(preferably 3-5 volts) and the lower volatge (0-3 volts).

Quoting pcmag.com,"Digital optical discs such as CDs and DVDs store binary data as microscopic variations in the height of the disc's surface, known as pits and lands. Bits are encoded as transitions between raised lands and etched pits, which are lined up in a spiral like the groove of an LP. On a mass-market replicated CD, this pattern is stamped into a 1.2-mm clear polycarbonate disc, which is then covered with a super thin coating of reflective metal (usually aluminum or gold) and a label."

This means that, on the surface of a disc, there would be the following features on a microscopic scale, a somewhat raised surface and a pit. In order to read from the disc, an infrared laser is beamed through the CD's polycarbonate substrate.