CD-R: CD-R stands for CD- Recordable. You can only record data onto a CD-R only once.
CD-RW: CD-RW stands for CD-ReWritable, and as the name suggests, you can record data any number of times onto a CD-RW(subject to wear and tear). CD-R is represented by two speeds (AxB), the former is the write speed and the latter is the read speed. The write speed is always higher than the read speed.
CD-Rs are of two types:
1. Single session and
1. Single session CD-R: A single session CD-R can be used for a single session of recording. The CD is closed after a single session of recording, and the remaining space on the CD becomes un-utilized.
2. Multi-session CD-R: Multi-session CD-R allows recording possible during multiple sessions resulting in efficient use of space. A multi-session CD-R can be closed after a single session if required.