A DVD Forum (the industry body that controls the development of DVD formats) approved re-writable DVD format. Format allows single-layer data to be stored on each side of the disc -- in other words, one side of the disc can hold upto 4.38 gigabytes of information (NOT 4.7GB what the disc labels claim -- 4.7GB is achieved by tweaking the numbers and using 1,000 in calculations between megabyte and gigabyte, when the correct number to be used should be 1,024). Dual-layer discs that could hold 8.5GB don't exist and most likely never will due technical limitations. This poses a problem when backing up pressed DVD-Video discs that can hold dual-layer worth of data per side, 8.5GB. Those discs need to be split to two DVD-RW discs if all the information has to be preserved from the original disc.
DVD-RW is technically slightly less advanced than its competitor, DVD+RW. But the year 2002's projections of blank media sales show that sales of DVD-RW media will dominate the markets with appx. 75 percent re-writable market share.
Both, DVD-RW and DVD+RW, formats are re-writable formats. DVD-RW's "sister format" is called DVD-R which is essentially a record-once version of DVD-RW. DVD+RW's sister format is called DVD+R.
DVD-RW discs can be read with virtually any PC DVD-ROM drive and with most of the regular, stand-alone DVD players.