A parked domain is NOT a unique website. Instead, it is a masked forward to the primary domain name of your cPanel account, much like a website alias. Parked domains are commonly used when you need a place to park a domain you do not have a website for, when you have more than one domain that should lead to your primary domain, or when you have common misspellings of your domain name that you have registered.
A subdomain is a second website, with its own unique content, but there is no new domain name. Instead, you use an existing domain name and change the www to another name. The subdomain name looks like forums.domain.com, help.domain.com, help2.domain.com (assuming you already host domain.com).
An addon domain is a second website, with its own unique content. This type 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.
About addon domains
Addon Domains are handled like subdomains as far as the server is concerned, but to the outside world they are separate domains.
Addon Domains do not have their own cPanel; however, you may still create e-mail accounts, redirects, Fantastico installations, subdomains, etc.
Web stats for your Addon Domain will be found within the icon of the web stat program you select in cPanel. If you are using an older cPanel theme such as “X”, you will need to look under Subdomain Stats to find the web stats.
Every addon domain is also a subdomain. You may actually load your addon domain in one of three ways:
http://addondomain.com/ (As an Addon Domain Name)
http://addondomain.com.primarydomain.com/ (As a Subdomain Name)
http://primarydomain.com/addondomain.com/ (As a subfolder)
Don’t worry! Visitors will only know the link you give them; they have no way of knowing which domain is your primary domain and which is the addon domain. To your visitors, the Addon Domain appears to have its own hosting plan.
Note: The temporary URL for an addon or subdomain is
http://ipaddress/~username/subfolder/ or http://servername/~username/subfolder/
where the username is your cPanel user name for your primary domain.
Many providers who provide cheap hosting services actually doesn’t host your domain in an real Linux hosting account, instead they purchase a Linux account with large hosting space and unlimited add-on domains. So in return of cheap hosting you are hosting your domains in the same account and your seo score can be ruined if the provider is hosting similar sites in same account. For example: you can check
http://www.aryabakery.com and http://edujini.net/aryabakery/ – an example of add-on domain.
http://www.sunflower-hotels.com and http://edujini.net/sunflower-hotels/ – another example of add-on domain.