Compact discs, or CDs, are a type of digital optical disc used to store data, primarily music. Introduced in the early 1980s, they revolutionized the way people listened to music by providing a high-quality audio format that was more durable than vinyl records and cassette tapes. A standard CD can hold about 700 megabytes of data or approximately 80 minutes of audio. CDs are read by a laser in a CD player, which interprets the digital information encoded in tiny pits on the disc's surface. Over time, the popularity of CDs has declined with the rise of digital downloads and streaming services, but they remain a significant part of music history and physical media collections.