When installing a modern Windows Server, you have the choice between two installation modes, core and some sort of GUI.
In fact there are four different levels of GUI tool support, in Server 2016 there will be five.
I call them operational modes and this page describes the differences between them.
Since Server 2012 you can switch between the modes, I recommend moving up or down one step only. Don't go from Core straight to Desktop'
As I see it, you will not be able to switch to and from Nano Server, because its deployment model is different from the other modes.
It seems this model changes with Server 2016. You have to pick the mode at installation time (either Nano, Core or Desktop) and can not change the mode later.
Min-Shell and Full-Shell no longer exist. Not a good choice in my opinion.
The various modes
Introduced with Server 2016, no local console or RDP host to log into. All administration has to be done remotely.
Only a limited set of roles and features are supported. Work in progess, the supported features may changed before RTM.
Introduced with Server 2008, sometimes described as gui-less, but does infact has the normal Windows GUI with certain components removed. This is the default option in 2012 R2 and 2016
Introduced with Server 2012, known as "Mininal Server Interface" has support for Server Manager and all MMC based administration tools.
This option is not available at install time for 2008 to 2012 R2, on Server 2016 this is no longer available.
To get to it from Server Core use:
What you get when using "Server with a GUI" on Server 2008-2012 R2, this is what most people still use. It has the desktop, File Explorer and Internet Explorer.
On Server 2016 this is no longer available
To add it from a Min-Shell run:
Install-WindowsFeature Server-Gui-Shell -restart
The desktop experience role, adds additional features from the workstation version of Windows including the Windows Store and modern apps. This is the second installation option for Server 2016
from Server 2012 and 2012 R2 but not 2016
To add it from Full-Shell: