An addon domain is a second website, with its own unique content. This type of domain does require you to register the new domain name before you can host it. So, if you want to host www.otherdomain.com, this is the solution.
A parked domain is NOT a unique website. Instead, it is a masked forward to the primary domain name of your web hosting account, much like a website alias.
Both of these features are offered with the Intrinsic One Plan Web Hosting.