Compact Disc ReWritable (CD-RW) is a rewritable CD that was introduced in 1988.
In theory a CD-RW disc can be written and erased roughly 1000 times, although in practice this number can be much lower. The main difference in the make up of CDR and CDRW is that decrystallization of CDRW media. This results in a shorter life span of the CDRW(25yrs) to the CDR format (30+ yrs)
CDRW have a limit on the allowed recording speed and unusually a minimum writing speed under which the disks cannot be reliably recorded. Generally Older CDRW burners that lack appropriate firmware and hardware cannot handle newer, high speed CD-RW disks, while newer drives can generally record to older CD-RW disks, provided their firmware can set the correct speed, delay and power settings for the task.