CD Rom is a standard disc reader. It will read the discs that install programs, music cd's, etc. A DVD RW is a drive that you can use to create DVD's. The RW means that it can READ and WRITE DVD's. So the same holds true to a CD-RW. It is a disc drive that can READ and WRITE CD's.
DVD-ROM means that it will simply read or play DVD's but not write or burn to a blank DVD disc
Most drives now I think are standard CDRW which means you can "burn" or transfer your music files, regular files to a disc.
DVD discs hold more information I think they are like 4gig. WHile CD's are only 700mb.
A DVDRW will only write to DVD discs and A CDR/W will only write to CD's.
Hope that helps. I use CNET.com for electronic purchases and for other info.
DVD = Digital Versatile Disc
DVD-ROM = DVD read only memory (like a pre-recorded movie DVD)
DVD-R, DVD+R = recordable DVDs, + and - are two different technologies but both are generally supported by current drives
DVD-RW, DVD+RW = rewriteable DVDs, also both generally supported
DVD+R DL = dual-layer recordable DVD, about double the capacity of non-dual-layer
The optical drives you can buy will state what they'll read and record, while also giving you a speed (given in xX, e.g. 16X DVD+R). This refers to the multiple of the original base speed (which was 1X, and in the case of DVD+R, was 1,385,000 bytes per second).
Computer DVD-ROM drives can all read CDs. If it isn't explicitly stated as also being a CD-R/W drive, all it can do is read DVDs and CDs. You'd need a CD R/W or DVD-+RW. DVD writers can also write CDs.