CD-R stands for Compact Disc-Recordable.

It is a type of CD that allows data to be recorded only once. After the information is recorded ("burned" by a laser), it becomes permanent and cannot be erased or rewritten.

Although it is possible to add more data in subsequent sessions if the disc is not "closed", the space already used cannot be recovered.

The CD-R was a very popular medium for creating custom music CDs, making backups, and distributing software. Its technical specifications are defined in the industry standard known as the "Orange Book."