WordPress.org

What does this plugin do, exactly?

1. For any image contained in a post that has been specified as linked to the image source (the default, e.g. a large image resized to 'medium' and linked to the larger version), add a rel attribute with the value facebox. This is accomplished as a filter on the_content.

2. Any linked content inside a shortcode gallery will demonstrate identical behaviour to those linked images in posts; viz., when clicked they will giggle and squee in delight, emitting sunshine and rainbow glitter.

Or, you know, a Facebook-style lightbox appears with the linked content.