A CD-RW, or Compact Disc ReWritable, is a type of optical disc that allows users to write and erase data multiple times. Unlike a standard CD-R, which can only be written once, a CD-RW can be reused, making it a flexible option for storing files, music, or backups. CD-RWs are compatible with most CD drives, but they may not work with all standard CD players. They typically hold up to 700 MB of data, similar to a CD-R, and are often used for temporary storage or transferring files between computers.