A "trailing slash" redirect is issued when the server receives a request for a URL http://servername/foo/dirname where dirname is a directory. Directories require a trailing slash, so mod_dir issues a redirect to http://servername/foo/dirname/.
Example :
DirectoryIndex index.html
Then a request for http://myserver/docs/ would return http://myserver/docs/index.html if it exists, or would list the directory if it did not.
