Minimal mode (Core mode)

Windows Server can be installed with a graphical interface (GUI) or without a graphical interface (which is called Core mode).
A minimal installation (or Core mode) of Windows Server allows you to benefit from a more efficient server, because :

• it's lighter : there are fewer source codes and fewer features available. No console with graphical interface, some roles are not available in Core mode, ...
• it uses less the resources of your server : hard drive, graphics card, ...
• it's less vulnerable to attack since the source code is simpler (shorter) than the version with a graphical interface

In short, in Core mode, you will be able to manage your server locally only from the command line (via cmd or PowerShell), via the integrated "sconfig.cmd" utility or remotely via the server manager and the usual RSAT consoles (although this requires a specific configuration in a workgroup or in an Active Directory domain).