Traditional CDs (about 16-20 tracks on a disc) use a different format (WAV?) that takes up far more space than the MP3 files we are so used to now.
It's been a while since I last ripped anything from my CD collection as I also buy via amazon nowadays and get the physical CD as well as a downloadable, ready converted MP3 copy. Before anyone asks, I like to own the physical copy as security against me accidently killing the hard drive I have my music stored on. Sure I have multiple copies of many of the albums dotted about on various devices but sods law dictates that should the worst happen I am bound to lose a couple of the hardest to replace or most favourite albums.
When you rip (copy and convert to MP3) the album you need to select an appropriate quality or bit-rate to ensure good sound reproduction. Too low and you will have tiny file sizes that allow you to fit more on a device, but at the cost of quality. I think you can start as low as 64(bps?) and go up in steps to 128, 256, and maybe 412 or more. I usually plump for 256 as file size isn't as critical now we are not trying to store them on CDs or DVDs.
Hope this helps
EDIT: If you purchase via amazon I think the downloads remain available to access as long as you keep your account, so if you do lose your e-copy somehow you haven't lost it and can just download it again.
