From David Raynes:
The workflow plugin is designed for users of Movable Type who require fine-grained control over which authors may publish content. Workflow allows you to grant publishing permission to only the authors you choose (editors), while other authors (contributors) may only save entries as drafts. Once satisfied with their entries, contributors can transfer their entries to an editor who may then publish the entry to the blog. Any author or editor in the system is notified by email when an entry is transferred to their ownership.