The script implements Dan Margulis' concept, The Bigger Hammer, from his book Modern Photoshop Color Workflow, Chapter 10. Please consult this book for examples and details on using the script. The script is useful for enhancing details in highlights and/or shadows.
There are already several plugins to creates paths with geometrical shapes, but they all require tedious entry of numbers in some dialog.
So this plugin uses a radically different method: the significant points are entered as points in a path stroke, and then the plugin us called without any explicit parameters (there is a menu entry for each shape/interpretation of the path, so they can be assigned to a keyboard shortcut).