CD-R

Also known as CD-WO (Write once) or WORM (Write Once Read Many) drive. CD-R is short for CD-Recordable and is a writable disc and drive that is capable of having information written to the disc once and then having that disc read many times after that. If the data is not written to the disc properly, has errors, or has the incorrect information that disc or portions of that disc cannot be erased and is often jokingly referred to as a coaster.
A CD-R disc is coated with a photosensitive organic dye that allows a user to record information. Once the CD-R disk is placed within the computer, the recording process begins. The laser inside the drive heats the dye to reveal the areas to diffuse light just as a traditional CD pit would. The CD-R drive does not actually create pits on the CD; instead the burner creates reflective sections on the CD causing the computer's CD-ROM laser to interpret it as a pit. Once a CD-R disk is finished recording, the CD will be able to be used in any standard CD-ROM, CD-R, CD-RW, or DVD drive. Although in the past there were issues with reading CD-R disks in the first revision of DVD drives.
CD-Rs are a low cost solution for backing up software. Each CD-R often only costs a few cents (as of 2010 around 17-cents a disc) and are capable of holding up to 650 MB (74 minutes of music) or 700MB (80 minutes of music). Although these are still a very popular solution for backing up data more users are turning to USB thumb drives to backup and transfer data.

Also see: Burn, CD, CD definitions, CDRFS, Coaster, R/W, Multiple sessions CD-R, Orange book, Rip, Storage