A modifier key on Windows keyboards that is pressed with a letter or digit key to command the computer. For example, holding down the Alt key and pressing F displays the File menu if it is a current option on screen. Pressing Alt-Tab toggles between active windows (see Alt-Tab). See Control key and Command key.
It's easy to set up your computer so that ordinary windows movement and resizing take place normally, but using the shift, control, or alt keys while moving or resizing windows results in stunning graphics effects.