Most CD-Rs claim to be for both audio and data (you always see 700 MB (data) / 80 minutes (audio). However, since audio CD players tend to be more picky at times, I would only use better quality CD-R for audio backups.
There are also audio CD-Rs that are specifically designed for standalone CD recorders (HiFi), they are often referred to as Audio CD-R. The standalone CD-recorder will, in principle, accept only these media (there is a work-around I heard). I don't know if these media can also be used on PC CD-R drives, but I would not do so...I would just stick with better quality data/audio CD-R as you would buy for your PC.