For example, If you where to put you're favorite songs on your Ipod, but then, accidentally delete them all off of your computer. So you sat there in a bad mood and it hit you, My Ipod still has all my music! I can just re-import in from my ipod! Thats when you would go into iTunes and see if you could drag them out of your Ipods library into your iTunes library, but no Apple didn't want to make it this easy for some obvious reasons.
But here is how you can do it Free without any software.