content-disposition is a:
that indicates to the user-agent (ie browser or email client) if the content (resource/body):
if ($download) {
header('Content-Disposition: attachment;' . rfc2231_encode('filename', \dokuwiki\Utf8\PhpString::basename($orig)) . ';');
} else {
header('Content-Disposition: inline;' . rfc2231_encode('filename', \dokuwiki\Utf8\PhpString::basename($orig)) . ';');
}
The body of an email may be directly the attachment.
Example:
Content-Disposition: attachment; filename="images.zip"