The ability to playback home-recorded DVDs.
DVD-R and DVD+R are write-once formats. You can record onto these discs once and they are non-erasable.
DVD-RW and DVD+RW are rewriteable discs. These discs can be erased and re-recorded about 1,000 times.
DVD-RAM is also rewriteable, but can be erased and re-recorded up to 100,000 times. Some DVD-RAM discs are encased in cartridges; compatibility here is for discs without cartridges.