everyone knows this, but for those who don't
An mp3 player is a sophisticated music player.It can be as small as a kids finger.Mp3 players had their origin from mp3 format of music.An Mp3 or an Mpeg 3 music format sound similar to normal music,but it isn't.When you convert normal music into mp3 format(with the help of computer softwares) it removes that part of the music which our ears cannot hear.Hence making it smaller in size.