Droplets work by tying a single action to a shortcut icon in your file system. When you drag and drop files onto a droplet, Photoshop opens in the background and runs whatever action you’ve configured it with.  With most Photo Booth Software, a script will tell the software to use the droplet and Photoshop does it’s magic.  Photoshop IS REQUIRED and MUST be running in the background for the droplet to work.  The actions recorded in the droplet will create the effect on the phots and then will save over the old version.  The process may take a a few seconds.  Of course, the better your computer, the faster the results.