Hello
A parked domain is an additional domain that points to main directory of your account. You can park an unlimited number of domains at no cost. A parked domain will resolve to your primary domain name.
Say your primary is abc.com and you park xyz.com
In the address bar if you type xyz.com it will resolve to abc.com but in the address bar you will see xyz.com.
An add on domain allows you to run a separate web site to your primary domain. When you create an add on domain, it makes a folder in your public_html folder and you upload the site content into that folder. So essentially you are running 2 separate sites, separate content, off one account. The Basic and Business plans now come with unlimited free addon domains. The Windows shared plan comes with 1 free add-on domain, and a second can be purchased for $2.50 per month, for a total of two.
Say your primary is abc.com and you create addon domain xyz.com. The addon domain is pointed to the xyz folder under public_html
In the address bar if you type xyz.com it will resolve to the content in the xyz folder and in the address bar you will see xyz.com.
With both the parked and add-on domains, you can create seperate email accounts for each domain name.
Thanks