Introduced in Windows 2000 as a way to shutdown the PC via the command prompt.
Included in all versions since Windows 2000 all the way to Windows 10 and Windows Server 2019.
ReactOS, the open source binary-compatible clone of Windows, also includes the shutdown.exe command and the commands are the same.
Located in %windir%\System32. The variable %windir% is usually c:\windows. In ReactOS, the variable is usually c:\reactos (failed to mention this in the recording).