highlighted and help regions I'm teaching myself Drupal theming, so naturally, one of the first things to think about with my (Zen) sub-theme are regions. However, the documentation is lacking in its explanation of the meaning of a couple of the defaults.

On the Assigning Content to Regions page, it says:


  Drupal 7 adds Highlighted and Help as default regions. By default, the textual content of the Help region is the same as the $help variable was in page.tpl.php for Drupal 6.


This is very bad copy, because it never actually states what these regions are for. And although the meaning of most of the regions (content, header, footer, the sidebars, etc.) is pretty obvious, I'm a bit fuzzy on the precise meanings of Highlighted and Help. Is Help the place where system messages (like the "theme cache is being rebuilt on every page view" message I get while I develop) are printed... or is that what Highlighted is for?
Basically:


$messages is where your system messages are put via drupal_set_message()
$help is created from http://api.drupal.org/api/drupal/modules%21help%21help.api.php/function/hook_help/7
and I have never used the mission statement stuff but apparently that's what the highlighted region is used for now and is described in greater detail in http://drupal.org/update/themes/6/7 which has a lot of information on the d6 -> d7 theme changes.