Audio Formats: MP4
MP4 files are a new compression standard that is higher quality than MP3. It is also known as AAC and used to store audio on all comercial DVDs. You should listen to these if you have the choice.
These files give you a better listening experience with a shorter download, but can only be played on computers with newer software. Quicktime 6 or later for mac or windows can play these files as well as some other types of software. You can download it (I recomend you do if you don't have it already) at http://www.apple.com/quicktime/. Chances are if you have a computer from the last one or two years you'll have this software.