OT: what's the point of mp3's?

[Krzys Majewski]

-rw-r--r--    1 krzys    krzys      118700 Jul 31 17:28 hip1302mp3.mp3
-rw-rw-r--    1 krzys    krzys     1308716 Aug  9 10:05 hip1302mp3.wav
-rw-rw-r--    1 krzys    krzys      117718 Aug  9 10:06 hip1302mp3.wav.gz

So what's the point of .mp3?  -chris