The WordPress XML for Feeds module exposes WordPress-specific data in WXR files (that's "WordPress eXtended RSS") to the Feeds module. It also includes the WordPress Importer module (a features-package), which imports WXR files using Feeds and the WordPress XML parser.
The purpose of the WordPress XML for Feeds (
wp_feeds) and WordPress Importer (
wp_feeds_wxr_importer) modules is to offer a comparable feature-set to the WordPress Import (
wordpress_import) module (not to be confused with WordPress Importer (
wp_feeds_wxr_importer) module), but in a way that is far more flexible, and that integrates with Feeds, CCK, FileField and other popular Drupal APIs so that data can be manipulated to fit arbitrary data models.
See also WordPress Migrate module, which I have not tried out. A comparison would be nice.