Recently asked a friend to pick up some pc discs for me while he was back in the uk i want to save photos audio and documents and be able to add to the discs as i go along the email i had from him asked if i wanted DVD or CD, R or RW i assume most or all of you will know what that means i dont i'm afraid what do i require

If price is an issue, always go for the shops own brand. They seem to be just as good. DVDRW are more expensive but that's because 4GB is a lot of space. For lots of music and films, An external hard drive or storage would also be cost effective rather than CD's. I tend to use USB's forstorage because of their size, but I did have an important one break once and it cost 60 quid to get my files back.

services like Dropbox will give you 2GB free of online storage

For data I use both CD-R and DVD-R. There is a big difference in capacity. On a CD-R you can store about 650-700 MB, and on a DVD-R about 4.7 GB (single layer). To add to the discs as you go along is called "multisessioning" and only after you are finished with the disk, you tell the burn program to "close the disk". RW discs can be erased and rewritten, but personally I don't see the point because -R media is so cheap nowadays.