There are literally dozens of different types of discs. The ones focused on in this site are laser discs--discs that use a laser to read and write information on (for example, compact discs - CDs).
Discs generally all work the same way, from CDs to Blu-ray discs, they all have a set of grooves 'cut' into the surface. A laser reads these grooves and translates them into I's and O's. Then whichever device you are using (like a CD player) translates the I's and O's into information.
Discs took the industry by storm in the early eighties. Originally used only for audio, they enabled manufactures to store high quality sound in a relatively small space. But what was most attractive to disc end users, was the fact that the disc did not wear with usage.
Later, manufacturers developed ways for end users to write to discs ...which would cause them to take the place of magnetic disc drives in computers. And soon, they went on to take the place of VCR tapes.
Of course, the DVDs were the original discs. Aside from the advantages mentioned above, they allowed viewers to interact more as they watched a movie. Viewers could turn subtitles on and off (something they couldn't do with a VCR tape). Viewers could quickly skip entire scenes (or even start in the middle of a movie without using rewind or fast forward buttons). And on top of all of that, a DVD could deliver a much sharper image than a VCR tape.
But like most things in any industry, there's always room for improvement. And that's why the Blu-Ray Disc was developed.
At first, there were two high definition formats in the industry. Like the VHS and Beta tapes, they competed for dominance. The two formats were Blu-Ray and HD DVD. You can read the section on Blu-Ray Discs to see how that played out. For now, suffice it to say that it looks like Blu-Ray is the winner.
Blu-ray discs don't do anything entirely new. They're more of an improvement on DVDs. They offer higher definition, and more interactivity. In short, they hold more information. This just offers the entertainment industry more room to get creative.
Of course, like DVDs and CDs, Blu-ray discs can be used to store any type of information or data. Their high capacity makes them perfect for the computer world, and writeable blu-ray discs are likely to take over the popularity of writeable DVDs within the next five years.
Click on the next arrow to find out how it all began with CDs, or