A parked domain is nothing but the alias of the main domain where it supposes to land to page of the main site. Parked domains can also refer to URLs that you register but don’t point towards any website in particular. Whatever you decide to do with your parked domain or alias, however, setting it up is downright simple.
Addon domain works as an individual site but situated under the control panel of the main site. No one can identify it as an addon domain, it mainly uses to host multiple sites under roof.