A Compact Disc-Recordable (CD-R) is a type of optical disc that allows users to write data onto it once. Unlike standard CDs, which can only be read, CD-Rs can store music, photos, and other files, making them useful for personal data storage and sharing. Once the data is written, it cannot be erased or modified. CD-Rs are compatible with most CD players and drives, making them a popular choice for creating custom music albums or backing up important files. They typically hold up to 700 MB of data or about 80 minutes of audio, providing a convenient solution for various storage needs.