I found this while on BestBuy.com, take a look:
DVD-RW: This is the rewritable DVD disc. These discs (like their CD-RW cousins) can be re-recorded up to 1,000 times. Like DVD-R, they can be played back in some DVD video players and all DVD drives.
DVD+RW: Another rewritable format, DVD+RW is the newest player in the recordable DVD market. When DVD+RW media is burned in a DVD+RW drive, they can be played back in most DVD video players and all DVD drives. The introduction of DVD+RW may cause some fragmentation in the market, though it is too early to tell what the impact might be.
Here is the URL that explains more DVD Media:
http://www.bestbuy.com/ComputersPeripherals/DrivesStorage/hr/hr5DVDRWdrive.asp
Hope I helped