DR MBarnum - As DR edisaurus just indicated, when you purchase and album from iTunes you are just purchasing digital music files of each song on the CD. -Consequently, for most CDs, you can also just purchase individual tracks. You do not receive and actual hard copy (CD disc). A lot of the iTunes offerings now offer digital booklets, and some iTunes releases will have special "iTunes only" content.
Personally, I still like buying real CDs, but when I've needed to listen/reference a song on short notice, iTunes has really come in handy.
*Of course, if you wish, after you download a CD, you can then burn a cop to a CD-ROM.