Click the 
button,
Or click the icon in the upper left corner of the title bar and select Minimize,
Or right-click the window title bar and then click Minimize,
Or press ALT+SPACEBAR+N (application) / ALT+HYPHEN+N (document).
Application/document control minimize reduces the application window or document window to a small icon at the bottom of the screen. To restore the window to its previous size, use the Application/ Document Control Restore command or double-click the icon.
To minimize the window:
Click the button,
Or click the icon in the upper left corner of the title bar and select Minimize,
Or right-click the window title bar and then click Minimize,
Or press ALT+SPACEBAR+N (application) / ALT+HYPHEN+N (document).