What's the difference between DVD+RW and DVD-RW?

[affie]

got this from THG,
"Archiving
If your main goal is to archive data, the DVD-R format (Pioneer DVR-A05 or TEAC DV-W50E) is the best choice. 4x burn speed gives you your result in 15 minutes. The time saved compared to DVD+R at 2.4x (over 24 minutes) is not to be sneezed at.
Video
However, if you are more interested in video, the DVD+RW format is still the best solution. It is much more flexible to use and, what's more, it is compatible with Philips home players."