Compact Disk Rewritable, n.: A CD that you can burn with various amounts of data multiple times or erased unlike a CD-R which can only be burned once and cannot be erased.
CD-RW have a much higher cost than CD-R's and slower burning rates and thus less used.
I prefer to use CD-RW for work because I can reuse them, but for permanent things I like to use CD-R.
By Doll
Cd-rw
A type of CD that can be written on AND erased. Somewhat like a regular computer floppy disk.