What rights do I have with music purchased through the Play Store? I was about to buy an album that Google Play recommended, and I thought was good. Just as I'm about to enter my password, I noticed that nowhere does it show what type of music I'm getting. Am I getting DRM-free files, or DRM-enabled files? What are the restrictions? Can I play it in my car through a USB flash drive, if they're MP3 files?

Where can I get information about the usage rights of music purchased through the Play Store?
Albums bought through Google Play show up in the Play Music app by default. The files from the Play Music app can only be played through that app itself, and can't be extracted. However, you can download music from the Google Play web interface as plain MP3 files, either individually or your whole collection in one download.

The official support site gives more details, and instructions on how to download.