Cd-rw

I'd appreciate it if someone would please enlighten me on this very basic tech topic:

How do CD-RW's compare to CD-R's? Do each hold about 80 minutes of music? Do CD-R's sound better than CD-RW's? Is there any limit as to how many times a CD-RW can be recorded over, and does sound quality decrease the more you record over it? Finally, is the fact that a CD-RW can be recorded over the only real difference between CD-R and CD-RW? Thanks.