Within cPanel, you have the ability to add either a Subdomain, Addon Domain, or a Parked domain. These different types all have their own fairly unique uses.
Generally a subdomain is an additional URL, which is based off the primary URL of the account. For example, with domain.com, you would use sub.domain.com, and specify where within your account you would like that to point to. This would allow you to have two individual websites, without paying for an additional domain.
An addon domain, is a method you use when you would like to utilise a Different domain to your primary, but have it completely separate from your website, and assign unique content.
You can specify which directory this can be located in, like you can with a subdomain, and it will have no relation to your existing site (unless you specify the same directory).
A parked domain is not an individual website, and is usually used to forward to the primary domain on the account.
Generally, you would couple this method with a 301 Redirect, to fully redirect any visitors of this domain to the primary one.
Standard reasons for utilising this method:
- You have a domain which doesn't have an active website, and you'd like to point it to an existing one.
- You have more than one domain which would relate to the same website.