Command+Tab
Try it!
Hold the command key down and don’t let go of it. Now press tab. Press tab again. Let go of command. WOW!!! You did it!!!
Now try this.
Hold the command key down and don’t let go of it. Now press tab. We’re not using that app, let’s quit it! Press Q (don’t let go of tab!). WOW! You quit it! Press tab again. Hmm, we don’t want to see that app. Press h. YOU HID IT!!!
How cool is that? 
Basically you were tabbing through your open applications. By pressing q the program was triggered to quit just as how pressing h made the program hide itself. To bring the hidden program back simply command+tab to it or click on its icon in the dock.
Pictures and a video coming soon. <3
