What is the www and public_html directory in my folder?

The public_html directory is the folder to place in web readable files. Files placed below the public_html folder will not be visable on the web. The www folder is what is called a symlink. This points to the public_html folder and generally is used as a shorthand is cgi scripts for the path. Instead of using the path /home/yourusername/public_html you can use /home/yourusername/www