Server Core is a minimal installation option introduced in Windows Server 2008 as a way to run Windows Server with a limited set of features and with support for only certain server roles. The Server Core installation option is available in the Standard, Enterprise and Datacenter editions of Windows Server 2008.
With Server Core, Microsoft stripped away all features (including the graphical user interface, or GUI) other than those essential to running core network services, such as Active Directory Domain Servers (AD DS), DNS, Dynamic Host Configuration Protocol (DHCP), and File and Print services.
The Windows Server Core installation stands in contrast to the full installation option for Windows Server, which supports installing all available server roles as well as other Microsoft and third-party server applications like Microsoft Exchange Server or SAP.
Server Core Supplanted by Nano Server in Windows Server 2016
While Nano Server shares similarities with the Server Core option in Windows Server 2008 and Windows Server 2012, Nano Server is even leaner than Server Core (twenty times smaller than Server Core) and is optimized for use with the modern cloud.