Parked Domains – Parked domains are domains that are registered but are not active websites. They are typically used as placeholders to reserve a domain name or redirect visitors to another website. Suppose your primary domain name is "yourdomain.com" then the name of your parked domain will be "yourdomain.net" or "yourdomain.org" or "yourdomain.info" etc. But the contents will be same as primary domain mentioned earlier.
Addon Domains – Addon domains are additional websites hosted on the same hosting account. They are separate websites that use the same web hosting account, but have different domain names.
Subdomains – Subdomains are subdirectories of a domain that are used to create separate websites within a main website. For example, if you have a website called example.com, you could create a subdomain called blog.example.com. Suppose you have a domain such as "www.yourdomain.com" and you want to create a subdomain then just replace "www" with your desired name as "sales.yourdomain.com", "test.yourdomain.com", "billing.yourdomain.com" and many more.
If your website does not contain www don't worry for that. It is not mendatory to have www as prefix of your website. To create a a sub domain you just need to give your desired name as the prefix of existing your domain.
