Commonly known as mp3, it is a common misconception that mp3 actually stands for "Mpeg 3". It doesn't, and there is also a version of Mpeg Audio called Mpeg Audio Layer II. The difference is that Layer III audio has better performance at low bitrates (i.e for streaming web audio). There is little quality difference between layers II and III at higher bitrates typically used in near CD-quality bitrates. Mp3 is a bit of a scam. I don't know how people believe that it is "CD quality" or similar - the sound is much blurrier than CD, and there are far better formats around. I recommend the QDesign Music CODEC for better results.