This module is responsible for making the Lua-based archive pages for the Refdesk at .
For all the recent archives like, it extracts the month, year, and desk from the title string if they are not otherwise specified. (The exact order doesn't matter; it does a text search) Therefore, these pages contain simply:
{{#invoke:RDIndex|month}}
However, conventional parameter-based settings are available to override the defaults thus obtained - however, these haven't been tested much and may need debugging.
doesn't do anything, because the text is read in by the module without template substitution - this module simply looks for {{Rdcat|xxx|xxx}} and processes it on its own. The first parameter sets a category for display in the table; the second is reserved for a subcategory system within a system.
Categories are things like "biology", "chemistry", "astronomy", "physics", "engineering" under Science. The subcategories would be more specific topics, perhaps evolution, DNA, protein, taxonomy, virology, etc. under Biology. To make the categories and subcategories work it is well-nigh essential to recruit people interested in sorting the questions, and for them to do so pretty consistently.