As noted for Drupal 5 in http://drupal.org/node/152458, Drupal 6 (head) similarly provides non-helpful links from the help text for the "Parent" and "Synonym" form elements on term add/edit pages (admin/content/taxonomy/edit/term/x). The page pointed to (admin/help/taxonomy) provides no help in understanding the terms 'parent' and 'synonym' in reference to taxonomy.
I have provided a patch that addresses the issue.
I'm not sure if my timing is right for this patch, given various freezes (code and string), and all. Feedback is always welcome. (I have a real desire to contribute, but hey, I'm still learning.)