iPODion is an iPod song browser and file ripper. Drag a mounted iPod onto it's icon, and iPODion loads the iPod's database file and gives you an interface for playing the songs on the iPod.
Unlike other iPod browsers, iPODium actually uses the iTunesDB file written by iTunes, giving it all the information included in the iTunes Library, not just the data stored in each song's ID3 tags.
It then displays this information in the familiar iTunes interface.
Why would you have a need for iPODion? Say you've brought your iPod to work with you, but your iTunes library is on a home computer. You want to listen to the music on your iPod with your work computer (this is especially useful for iPod Shuffle owners). If you plug that iPod into your work computer, you can't easily get at the songs on the iPod.
iTunes will complain that the iPod was not synced with this computer, and then want to erase all your songs. There is no provision in iTunes for playing the contents of a forign iPod. iPODion will play the songs straight off your iPod's drive, or you can use it to copy the songs to your own hard drive. iPODion makes it as simple as selecting songs in the playlist, and dragging them to the new location.