The main difference between the original feature in iTunes and Mojo is the fact that Mojo allows you to share music over the Internet too.
The other important difference is that Mjo lets you download tracks automatically if you want.
If you are listening to some tracks you like a lot, you can decide to download them and have them in your computer for the next time.
Add your friends to the list an d enjoy sharing your music. Listen to the music your friends listen to and enjoy this amazing application called Mojo.