Digital Music Primer
WSJ has a primer by Walter Mossberg and Katherine Boehret.
The main difference is that Apple has created an entire end-to-end digital media system around the iPod, and it works. In our view, and those of most other reviewers, the combination of the iPod’s design, the iTunes music software, and the iTunes Music Store, provides a superior experience to buying a player separately, using software from Microsoft, and buying music from an unaffiliated store.
As a result, the iPod, and the iTunes store, dominate the legal music world, with shares of more than 70% of the market, depending on how you measure it.