A document directory will probably have several subdirectories. For example, there might be a directory called products, another called people, and so on. It’s often helpful to let clients access an overview (or index) of these directories.
The server indexes directories by searching the directory for an index file called index.html or home.html, which is a file you create and maintain as an overview of the directory’s contents. For more information, see the previous section, Entering an Index Filename. You can specify any file as an index file for a directory by naming it one of these default names, which means you can also use a CGI program as an index if CGI is activated.
If an index file is not found, the server generates an index file that lists all the files in the document root.
If your server is outside the firewall, turn off directory indexing to ensure that your directory structure and filenames are not accessible.