Well you can customize them so you can have it open an application of your choosing or maximize a window. On the handle you have a +/- and these are your hardware volume control. On the right of that you have your >>/<< buttons and that's to Previous or Next on a media player or while watching a DVD. This works in iTunes also^^

You have a middle click button which is your wheel and you can customize your middle click button so it can scroll documents or whatever you want through the menu. The site i posted should tell you more into it. The one thing it should mention that in order to use your Back and Forward buttons in FireFox is to set them as Generic Buttons.

If you do decide to get this most beatrix let me know, i can tell you more in depth about them^^