I have just realised if you have two apps open and you 'alt + click' the 'bottom' app the currently active app is hidden and the bottom app becomes active.
If you have loads of apps open and you want a quick way to clear the crap off your desktop without quitting/minimizing apps just 'alt + click' all the apps one by one until they are all hidden and the app you want to use is left in all its glory.
Maybe you all already knew that. I didnt
just thought I would share! 
If you have loads of apps open and you want a quick way to clear the crap off your desktop without quitting/minimizing apps just 'alt + click' all the apps one by one until they are all hidden and the app you want to use is left in all its glory.
Maybe you all already knew that. I didnt