What is the Windows Key in the Computer, and What does it Do?
The Windows key is the name of a key on the keyboard with the Microsoft Windows logo printed on it that opens the start menu when pressed.
It's also used as a modifier key in keyboard shortcuts related to the operating system. By convention, applications do not use it for their own shortcuts. For example, Windows Key+D reveals the desktop. Windows key+Down minimizes the active window. Windows key+Up maximizes.

Where is the Windows Key on the Keyboard?
The left Windows key located between the Ctrl and Alt keys on the left side of the alphanumeric area. The right Windows key is between right Alt and Menu key on the right side.

Other Names
The Windows key is also called WinKey.

On Linux, the Windows key is called Super key, Meta key, or Hyper key.