CD-ROM, CDR, CDRW and CD Writer defined

CD ROM - Compact Disc Read Only Memory
This is similar to an audio CD and works in much the same way, but stores data instead of music (although technically, stored music is data). A typical data CD can store up to 700Mb, 486 times more information than a standard 1.44Mb 3.5" floppy disk.
A CD Writer (cd burner) can save data or audio to a special type of recordable CD (CDR or CDRW), this is an excellent way of backing up your data or creating audio CDs.

Although portable storage, such as the external hard drive, is a very convenient way to backup your data, a CDR offers that extra bit of reliability, hard drives can fail.

You will often see CD Writers advertised as 48X-12X-50X, this means it will burn (write) at 48X, ReWrite (write again over an existing rewritable CD) at 12X, and read at 50X the normal CD speed.

For instance, a 48X CD Writer will write a CD 48 times faster than normal (700MB in just under 2 mins).

CDR (Compact Disc-Recordable) refers to a recordable CD ideal for backing up data. Although, normal CDRs can be used to create audio CDs, there are special audio CDRs which offer a higher quality of audio reproduction.

CDRW (Compact Disc Re-Writable) refers to a recordable CD which allows the data to be overwritten numerous times (handy for daily back-ups).