Would someone please once and for all give a clear definition of all of these DVD formats and possibly why there are so many? Thank you.

DVD R
DVD-R
DVD+R
DVD RW

Any more I don't know about?

As far as I know DVD-R ; DVD R; and DVD+R are all the same thing. And with DVD-R's once you burn them the DVD is final, you can't go back over it and burn something else later. Also, I thought DVD RW and DVD+RW were the same type of discs in that you can go back over them and burn something else later if you want to. I could be wrong this is just what I always thought. If there is a difference I would also like to know. This may not actually answer your question its just my two cents.

The DVD Forum site (http://www.dvdforum.org/forum.shtml) offers answers to these and other questions.

Just incase people dont look other places for info.

DVD R: could be either +- as people dont tend to write it like that. Have to see it in context of a question or whatever.

DVD-R & DVD+R are NOT the same at all.
DVD-RW & DVD+RW are NOT the same either.

DVD-R & DVD-RW are the same family.
DVD+R & DVD+RW are the same family.

DVD-R can can come in DVD-R(G) General & DVD-R(A) Authoring formats. An authoring drive is required to write Authoring discs.

DVD+R drive cannot write a DVD-R and a DVD-R drive cannot write a DVD+R but there are now combo -+R drives that can write both types of media.

Just some added info,

Jake