CD-R
full spelling ： Compact Disk Recordable
CDR is a CD in which you can write data only once. Once you write data, the data is impossible to erase. There are two kinds of capacity; Once is the same capacity as an ordinary CD (650MB: 74 minutes of music), and the other is recently introduced one. (700MB: 80 minutes of music). CDR has organic pigments such as gold, blue, or green on the recording side and it records the data by radiating laser beam on those. The burn corresponds to the pits of normal CD. The way to read data is the same as CD. It reads the data by radiating laser beam on the surface of CD and reading the reflected light. CD and CD-R has the same way to read, so it is possible to read CD-R with CD drive, and also to play CD-R of music recorded by PC with CD player.
When CD-R was born at first, it was mainly used for business purpose because Media and Drive were both expensive. It was used to make master copy of CD-ROM or back up important documents in companies. These days CD-R has got cheap enough for an ordinary person to buy it, so it is used to make his original music CD or back up or exchange software or data.