Welcome to the Lightroom Queen Forums! We're a friendly bunch, so please feel free to register and join in the conversation. If you're not familiar with forums, you'll find step by step instructions on how to post your first thread under Help at the bottom of the page. You're also welcome to download our free Lightroom Quick Start eBooks and explore our other FAQ resources.
Yes, it's a method of exposing PS 'actions' (like macros or scripts) externally to PS. That is making those functions accesible at the Finder/OS level, or for other applications.
In Victoria's book search for 'Photoshop Actions' in Chapter 8.
More exactly, in Photoshop, you can record your actions and name them as a set of actions. You can also export them as an executable called a droplet. From there, you can take an image in Finder/Explorer and "drop" it onto the said droplet; This will make Photoshop open with the image and execute the sequence of recorded actions on it. Also, you can add those droplets as external editors to Lightroom to send images to them from Lightroom...