A big subject simplified: "Most media are protected by copyright, but have a fair use clause which allows for unhampered use in certain situations. All existing DRM (Digital Rights Management)technologies fail to adequately make concessions for fair use, leading many civil advocates to argue that they restrict the legal use of content."
Basically DRM limites the copies you can make and requries that a licence file accompanies the song. Such as the case when Windows Media PLayer searches for the accompanying licence file in order to play the song.
DRM free means fair use, it means you can burn it to whatever you want as many times as you want, you can tape it, store it in your PC or even share it with others as it is not licence restricted. Mind you, SHARING music files is nto considered "fair use" whereas copying it for your own cdplayer, car stereo, computer etc. IS fair use. This fair usage is exactly how Canadians get away with file sharing, a law was passed here to allow fair use of media, making it next to impossible to sue Canadians for sharing files.
It is legal to have the file, legal to make copies for FAIR use, and legal to store them on your PC, it is also legal to run file sharing software on your PC. So if someone enters your shared folder with your stored, legal music, through a legal portal, it's prety hard to sue them.
IF you manage to work around all those issues and still want to sue a Canadian, then the supreme Court justice has already declared that an ISP offeringuser information is a breach of Constitutional Privacy Rights, so the ISp doesn't cough up the info, they are better off facing a small fine from the RIAA instead.
When you look at how the MPAA (Motion Pitcure Association of America) has now used open source software and then distributed it illegally with hidden code to track university kids downloadign films, you know they are just going too far, grasping at straws etc. Now the MPAA has breached a copyright themselves by not providing source code to their spy projects, so they have been told to cease and desist the rollout.
More info on that here: http://www.audioholics.com/news/industry-news/mpaa-dmca-takedown-notice
Looks like nobody has a clue how to keep gouging the consumers these days.