Websites commonly use directories or folders to organize the website files. Typical directories are css, images, and includes. Can people look at what is in your directories? Try this: your-domain.com/images/ and see if you get a list of files.
It could be a security issue if people can see into the directories of your website and select files to see. It is normally a better situation to prevent people from seeing your directories.
There are various ways to deal with this situation.
Here is one government site where you can see the list of images:
Depending on many factors, you might get an error message like this:
You don't have permission to access /images/ on this server.
One way to deal with the situation is to add an index.htm or index.html file to the directory and display an error message.
I do not care for any of these scenarios.
I create the following kinds of redirect statements in the .htaccess file.
Follow the link to see one example:
http://www.wizard-creek.com/images/ trying to look at the directory will send you to the home page.