If you want to host a website besides your primary domain name, you can use cPanel's Addon domain feature.
Addon Domains are only available for Deluxe and Ultimate cPanel shared hosting accounts. For more information, see What type of hosting account do I have?
Adding domains to your cPanel account simultaneously creates FTP users for the domain name. This FTP user has access to the domain name's Document Root and all of its subdirectories, but nothing above it.