"altKeyDown" command works just like you are pressing alt key of your keyboard. It will keep pressed alt key until "altKeyUp" not executed. You can use this command when you need to perform any action by pressing alt key.
Let me show you use of "altKeyDown" command with example. In bellow given example, altKeyDown command will press and hold alt key down then click command will click on targeted element.
|click||css=#gb_2 > span.gbts|
"altKeyUp" will release the pressed alt key. In above example, altKeyUp command will release pressed alt key using altKeyDown command.