A Real Time-Saver: Alt-Tab Keyboard Shortcut
Alt-Tab is the name for a keyboard shortcut on Microsoft Windows used for switching between windows without using the mouse.
If you press ALT+TAB to switch between Windows-based applications, Windows displays a box that identifies the last application that you accessed. If you hold the ALT key down, pressing TAB cycles through all of the applications that are currently running. When you let go of the ALT key, the identified application becomes the active application.