The compact disc (CD) is an optical disc storage format introduced in 1982. Like the LaserDisc, the compact disc was quite the revolutionary invention, perhaps even more so than the innovative LaserDisc itself in many ways. For starters, the compact disc is much lighter, more portable, and more compact than the LaserDisc (future optical disc technologies like the DVD and later Blu-Ray were built off of the compact disc standard and come in the same sizes as the compact disc). This of course resulted in portable CD players becoming a thing, as well as car CD players (much like what was seen with cassette tapes). The compact disc was also the very first optical disc to utilize digital audio (unlike the LaserDisc which used analog audio).
Then, in the 1990s, CDs were able to prove themselves to be more useful than competing formats with the rise of the average consumer demographic purchasing computers and CD burning software becoming viable, leading to the CD-R and CD-RW formats. CD-ROM interactive computer games and disc operating systems (such as MS-DOS) also helped the compact disc skyrocket in popularity. CD sales were booming throughout the decade and reached their ultimate peak in the year 2000. By the 2000s, CD players had already replaced cassette players in cars.
Despite CD sales slowly declining with the rise of MP3 players (and later subscription streaming services), CDs are still being produced and sold to this day and are used for storing things such as songs, photos, and computer games. Video CDs are also a thing (introduced in 1993), though they failed to gain popularity outside of some Asian countries where they remain cheaper than the price of a DVD (introduced just a few years later in 1996). Many fellow physical media collectors I've met are still into collecting CDs, so I have some hope for a possible CD revival in the near future (especially given all the ways in which CDs are superior to vinyl, which I'm not even sure as to why people even thought to bring that back given the many advantages of the comapct disc over vinyl). Hell, I've burned a few mix CDs quite recently and encourage others to do the same.
The average CD holds around 700 MB of data, which is about 80 minutes worth of audio, though miniCDs can only hold around 210 MB (24 minutes of audio).
