Sub Domains: If you have a domain name of your own for websites then you can create subdomains which will work as a separate website. You need not purchase a new domain name. In the example, the portion www is basically the subdomain and it is also called naked domain name. For example if you are building a website where users can have the sign in facility to create their own profile on your sight and the user members are invited by you to submit their articles or take part in forum discussions or ask questions then in the cited example we will change www to Articles, Forums or Experts (for question answers) so as to create subdomain as articles.example.com, forums.example.com or experts.com. Subdomains on your top-level domain can be added or deleted through the control panel or cPanel provided by your hosting service provider. Our main site www.webquestionanswers.com under construction will be having all these facilities to get your work or articles published, take part in healthy forum discussions and ask questions to be answered by our super experts in the respective fields. There is only one limitation to use of subdomains like www, mail, FTP, Cpanel, webmail. If you are to set up a mail system in the TLD then as per your hosting services provider you can create a subdomain like webmail.example.com. Subdomains do not require any registration and the very creation within TLD is sufficient.
Add on Domains: If the likely content on the subdomain is heavy and you feel like to host your content which is different from the above domain and does not fit into any subdomain then you can have add-on domain names which will require registration. Thus, if you want to host www.anotherdomain.com, then it is treated as Add-On Domain Names and it will depend upon the hosting plan taken by you as if it is for hosting one domain name, a limited number of domain names or unlimited domain names and every domain name will require registration.
Parked Domains: When you have registered a domain name but no website is hosted on the domain. For example, you have registered a domain name with wrong spelling then you can mask this domain name and redirect it to your primary domain name. Parked domains are not a unique website. If you do not renew your domain registration then your domain name goes to Parked State
