Views: Method click_sort() AND "Sort criteria" AND Custom views_handler_sort

Hi

I have a couple of questions dealing with Views 2 sorting functionality:

1. hook_views_data() AND sort attribute

If I declare a within view element declaration within an implementation of hook_views_data() as sort attribute, with what functionality is the handler views_handler_sort?

1. To view hander' method click_sort()?
2. To Views 2 UI Sort criteria functionality?
3. Both?

  $data['table']['column'] = array(
        // other declarations...
        'sort' => array(
          'handler' => 'views_handler_sort',
        ),
      );

2. Views 2 UI Sort criteria

Is Views 2 UI Sort criteria only meant for sort pre-rendering of the entire view and NOT for click sorting a column?

3. Custom Sorting Article(s)

Does anybody know about ANY good articles pertaining in implementing custom method click_sort() OR custom views_handler_sort?

Thanks

Jeff in Seattle