AirPlay is a function implemented by Apple since iOS 4.2 which allow iDevice owners to stream audio/video from an iDevice to a Mac. Officially, Apple supports this function only under certain conditions, but an addon for Media Center enables interaction with AirPlay. By installing Apple's Bonjour service together with the Media Center addon, you will be able to stream video and photos from your iDevice. We can't stream songs yet, but probably in the near future there will be an addon that will do this for us.
You can download the Bonjour service from here and you can download the addon for Windows Media Center from here. You install both and then you can stream without problems over a Wi-Fi network.
