Audio File Formats
MP3 is the most widely-supported audio file format. If you’re not sure which format to get, it’s the safest bet. The MP3s sold here are encoded at the highest possible quality, 320kbps.
AAC files sound better than MP3s. They work in iTunes (both Windows and Mac), and should work with most modern mobile devices. AAC is the iTunes store download format (“iTunes Plus”). These files might not work with old and/or off-brand mp3 players. If in doubt, check your device’s manual or search the web.
Apple Lossless (Mac) and FLAC (Windows) are “audiophile” lossless formats which provide CD-quality sound. The tradeoff is that they take up more space on your device than AAC or MP3 files.