Having a listable directories on your site sometimes is useful. However, some times it can be considered a security issue. No, matter which option you prefer you can control this behavior of your site using 1 simple line:
The above line enables Directory listing.
The above disables directory listing for your web site.
The .htaccess file gives more then simply enabling and disabling of a directory listing.
With .htaccess file you can control which files to be ignored when creating a directory list.
IndexIgnore *.gif *.zip *.txt
Will make the apache server to skip all gif, zip and txt files from the directory list.
Convenient, isn’t it.
Will just create an empty directory list.