MP3 is a compression form (like .zip) and stands for Mpeg 1 Audio Layer 3.
MP3 shrinks audio files in such a way that CD SOUND QUALITY is preserved, but the file size is significantly smaller than it would be as a regular CD song file. The size of a 4 minute song is reduced from over 40MB to less than 4MB.
This reduction in size (approximately 12 times smaller than the original) has several advantages:
1. Music can now be easily transmitted over the internet. The reduced file size means you can download an entire song in only a few minutes. Then you can play the song instantly as many times as you want - without requiring connection to the internet.
2. You can create CDs that contain over 160 songs and can play for over 14 hours.
3. Songs can be stored on a hard disk and played directly from there.
The MP3 format must be decompressed when played. That means that you need a computer and MP3 player to play them.