Home Sharing is what Apple offers to help all your device work with each other while all connected to the same network and Apple ID. Apple allows you to enable Home Sharing on up to five different computers. When it is enabled on your computers you can drag and drop your songs between different computers in iTunes and stream music and videos from other devices on the network.
Some of the major benefits of Home Sharing come if you have an iPad, iPod touch, or iPhone. When you enable it you are able to browse your entire music and video collection on your device and play them without syncing the content to the device. This also works on the Apple TV 2 and that is how you can stream all your content to the TV without the box having a hard drive.
Check out the video above to see how this is done.
Apple: Home Sharing