A sub domain lets you keep apart of your website seperate from the rest. We have seen this with shopping carts, sales sites, different languages or locations. For example in the Url “http://windsor.kijiji.ca/,”
the subdomain is “Windsor” of the main site “http://kijiji.ca.”
Add-on Domains let you have more that one domain on each hosting account.
go to cpanel–> Subdomain
Add the name of the subdomain and “Document root” will populate automatically. The “Document root” is the name of the folder that all of the subdomain files will kept in.
Add on Domain
cpanel–> add on domains
enter new domain name.
Hope this helps. Let me know in the comments section if you came across any problems.