Windows Server Core is a subset of Windows Server 2008 dedicated to a specific mission. If you want to setup a DNS Server, a File Server, or a Media Server you don't need to full blown Windows Server machine. You don't need the Windows Shell, You don't need sound capabilities, you don't need ... you have got the idea. Using a subset of Windows Server 2008 results a smaller memory footprint, faster server and smaller attack service. For example comparing to the full Windows Server...