DVD-RW and DVD+RW

I mistakenly thought there was a similar division amongst CDs ie CD-RW and CD+RW but it seems there isn't.

What the distinction is between DVD-RW and DVD+RW is not clear but see the Wikipedia articles:

DVD-RW
DVD+RW

They seem to be competing formats. cdfreaks has an article from June 2003 Why DVD+R(W) is superior to DVD-R(W) (it's a bit technical:).