I believe this is to allow you to start your computer from a Mac OS X install disc on a remote computer. You will need to connect to your wireless network to see the available discs.
I think this feature was more useful for original MacBook Air and/or for installing Snow Leopard. Since the new MBAs come with a USB drive, and Lion is expected (or at least rumored) to be distributed as an App Store download, you probably won't need to use it at all.