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There are several competing DVD Formats:
DVD drives from 2004 should be able to read either of the competing recordable formats, older drives may favour DVD-R discs. Modern drives (certainly at time of writing in 2007) typically allow writing to both DVD-R[W] and DVD+R[W] discs making the difference largely irrelevant to the average consumer.
VR Mode, also known as Video Recording mode, is a new format that allows editing and deleting of titles and has defect management. This mode is used by the DVD-RAM and DVD-RW formats. Because it is newer than DVD Video mode, it can only be played back in modern DVD Players that support it.
Video mode is the standard DVD Video mode format used by DVD movies. Because the DVD Video format was invented before DVDs were recordable it doesn't allow editing of the disc, doesn't support defect management and is therefore not as robust. Space from deleted titles may not be fully reclaimed until the disc is completely erased. It is compatible with most DVD players. It is used on DVD-RW and DVD-R discs, but has never used for DVD-RAM. Most (but not all) recorders that use DVD-RW will offer the choice of VR mode or Video mode.
+VR was introduced by Philips for use on DVD+RW. The idea was to maintain compatibility with the DVD Video format so it could be played elsewhere, but try and introduce some features as found in the VR mode used on DVD-RW/DVD-RAM. DVD+RW normally uses this mode in set-top recorders. It doesn't need a separate finalise step to play in other DVD recorders; finalisation is just done in the background, which makes it bit easier to use (i.e. you can't forget to do it), but it does put extra wear on the disc, as the same area of the disc is updated every time it is used. Due to DVD-Video not being able to take advantage of defect management and the extra overhead of background finalising after each edit or recording, the +VR mode has always been the least reliable, and the editing features may be missing on some DVD recorders to make it more robust.
Because Video Mode and VR mode are Forum standards, they are only used when recording to DVD approved formats i.e. DVD-RAM/DVD-RW/DVD-R discs. DVD+RW isn't approved by the DVD Forum and manufacturers can't get a license for it to use the above modes, leading Philips to introducing their own +VR mode for use with DVD+RW.