The Field Permissions module allows administrators to control who sees fields for your content types. For example, you might have a Content Type that captures an email address for the requestor, but you don’t want that information available to all people who view the site. Field permissions allows you to control which roles can view the content even when the page is published.
Drupal Gardens has a great tutorial on the specifics of how this module works. Click on the link in the Right sidebar to view more details.