DVD rw or CD rw

[Zeppelin]

Can anybody explain the differences between the two please

I know with a CD RW, you can store files, music etc onto a disc.
So these DVD RW:

1. Are they purely for recording movies?
2. Can they also store files/music?
3. Are the discs interchangable with each system
4. Whats the differance between the 2 discs

DVD RW seem to be a fairly new(?) thing, so for music/file storage is CD still the best way?

Might all sound stupid to the 'buffs' but to me a CD and DVD disc look exactly the same!

Thanks for any replies