Minimize and restore windows
When a window is active (its taskbar button is highlighted), clicking its taskbar button minimizes the window. That means that the window disappears from the desktop. Minimizing a window doesn't close it or delete its contents—it temporarily removes it from the desktop.
In the picture below, Calculator is minimized, but not closed. You can tell it's still running because it has a button on the taskbar.
Minimizing Calculator leaves only its taskbar button visible
You can also minimize a window by clicking the minimize button in the upper-right corner of the window.
Minimize button (left)
To restore a minimized window (make it show up again on the desktop), click its taskbar button. For more information about these buttons, see Working with windows.