I want to start buying my music from online download stores, but I've been told to avoid sites that use DRM. What is DRM and why should I avoid it?
DRM stands for 'digital rights management', and is a technology used by record labels and online music stores to limit what you can and can't do with the music you buy from them. For example, Apple uses DRM called 'Fair Play' that rather unfairly only lets you play songs from its iTunes store on its iPod music players. They won't play on any other device in the world.
DRM was introduced to combat illegal file sharing over networks such as LimeWire and BitTorrent. Putting DRM in every song sold legally means only you can play that file. If someone else downloads it over a P2P application, it simply won't play.
DRM is restrictive. Even though digital albums cost as much as a CD from the shops, you're given only a tiny portion of the freedom with that purchase. More annoyingly still is that CDs don't have DRM -- you're able to rip it, share it illegally, give it to friends, copy it to multiple devices and on to compilation CDs you make.
Sites such as eMusic don't use DRM, but this means only music from smaller, lesser-known bands are available to buy from it. At the moment, if you want legal downloads from big bands, you're going to have it covered in DRM. Some stores are slowly beginning to see the light and offer DRM-free downloads -- both and offer EMI's entire catalogue without DRM -- but it'll be a while before you can get that Eminem album without crippling restrictions. It depends if the other major record labels sign DRM-free deals.
The best way to avoid DRM is to buy the CD and rip it yourself. This is much less convenient, hence why so many people download illegally, but buying CDs is the only viable way of avoiding DRM and still supporting the musicians you care about. Plus you get the liner notes.
If you choose to buy protected music, make sure you buy a player that's compatible. iPods only work with protected music from the iTunes Store (or music ripped from CD), so you can't use them to play music from Napster. Conversely, music from Napster will only play on devices that support Microsoft's 'Plays For Sure' DRM -- such as the-- and no Napster tracks will play on an iPod.
The best advice is to choose your player wisely, or just buy CDs -- best of luck.