It allows you to select faces/edges/verts, store them into a buffer, select other faces/edges/verts and do a boolean on the selection
Example:
Select all faces with a particular area
Put that selection in the buffer
Select all faces with similar perimeter
Subtract that selection from the buffered selection
This addon has now been added to the default available addons when you download blender (daily and future release versions)
No need to download it anymore.
How about that!