XSKey - what is it?

This may seem like a silly newb question but bear with me please...

I have Logic Pro 8 - upgraded from Logic Express 7. Everything works fine and I love the program.

I notice in Apple's utility folder there is an XSKey Updater program. It has something to do with Logic but I have no idea what. I don't have one and my software did not come with one.

What is it? Do I need it? And if so, how do I get one? I can't seem to find anything about the key in the user manual.