Why is mp3 music easy to download?

mp3 is just one of the digital formats that music comes it. one of the main reason that it is easy is that it does not download all of the music. as it is digitally converted to the mp3 format, it is electronically altered so that some of the hi and lo frequency notes are removed as the files are compressed. that is why when you listen to mp3, you don't get the full rich sound you get from either the cd or from a live music braodcast