What are CD-R/CD-RW?

CD-R, writable CD.
CD-RW, re-writable CD. I think re-writable's are more useful, but if you don't want to edit and re-save what you put on it, either will do fine. Re-writables are obviously normally more expensive, but not prohibitively so. Can be more important when writing audio files, as some players, such as my xbox, will only play music that's been copied onto re-writable CD's.

Thank you Wilso!

For backing up photo files I would recommend CD-R. They are cheaper. They record faster and they are more reliable than CD-RW.

Use CD-RW only when you want to change the data often.