Do you ever need quick access to some of your running application's features, but don't want to open the the full window to access them? On some apps, you can access some of it's available features from the dock. The program must be running to do this. I am showing you with iTunes, but most programs support this, you just need to play around with it, and see what each app supports. Here is how: 'Click' on a dock icon (one that is running.. it will have a black triangle below it), and 'hold the mouse button down' . A contextual menu will appear, with options you can access. Alternatively, you can press 'Control' and 'Click' the mouse, and you will get the same menu.