New taxonomy template
The only template file used from the Taxonomy module is the taxonomy-term.tpl.php file. If a theme implement that template file, it receive the following variables. (The list is partial; for the complete list see the documentation.)


$term_url: Direct URL of the current term
$term_name: Name of the current term
$term: Full term object


page--taxonomy.tpl.php is a page template that Drupal uses for pages with a URL matching taxonomy/*. It is a page template, for which the variables are different. In particular, it doesn't get any $term* variable.

References


taxonomy_theme()
theme_get_suggestions()