Microsoft Windows is a GUI operating system created by Microsoft. The earliest version was a graphical shell on top of Microsoft DOS.
Desktop
Windows on desktop is the majority of the market due to its ease of use.
Server
The Microsoft Windows Server is popular due to the Active Directory system which allows admins to configure all connected desktops.
IoT (Embedded)
The Windows IoT, formerly Windows Embedded, is designed to run on low power computers.
Xbox
The Xbox One game console runs a version of Windows 10.