iTunes Tracker is a client which connects to a server maintaining a list of iTunes shared library addresses. This list is displayed on your computer allowing you to access any of the shared iTunes library on the list.
For iTunes 4.0 ONLY.
iTunes Tracker detects if you’re sharing your iTunes library.
If your library is shared then your address is added to the list of shared iTunes libraries. This list is what is downloaded when a client connects to the central server.