gecko-dev/extensions/python/xpcom/components

This directory is for Python implemented components that ship with pyxpcom

The .py files in this directory will end up on the XPCOM "components" 
directory, while .idl files etc will be compiled and installed as normal.

Of note:

* pyabout.py allows you to type open the URL "about:python" and have
  information about the local Python build displayed.

Most other files not listed are probably used internally and not worth
paying attention to!