The directory to import image nodes from. Drupal will need to have write access to this directory so we can move the file.
Note: a path begining with a / indicates the path is relative to the server's root, not the website's root. One starting without a / specifies a path relative to Drupal's root. For example: /tmp/image would be the temp directory off the root while tmp/image would be inside Drupal's directory.