A CD-R, or Compact Disc-Recordable, is a type of optical disc that allows users to write data onto it once. Unlike standard CDs, which are pre-recorded, CD-Rs can be used to store music, documents, and other files. Once data is written, it cannot be erased or modified, making it a reliable option for permanent storage. CD-Rs are commonly used for creating music albums, backing up important files, and sharing data. They typically hold up to 700 MB of information, which is equivalent to about 80 minutes of audio. CD-Rs require a compatible CD burner to write data onto the disc.