essentially it is a navigation bar that you can set to come up from the sides, bottom or top and be gone the rest of the time. I have mine comeing from the bottom so I have full screen for everything and my home, back and apps buttons are hidden. Then if I need them I simply slide my finger up and it pops up a pie like interface with the buttons. You can look in the market, PIE is in there. There are others, like button saver as well.You can hide existing buttons with a build.prop edit. "qemu.hw.mainkeys=1" and a reboot. Make sure you install the alternate button program before you do this.
I did this so I didn't have burn in down there and extra screen real estate. WOrks quite well.