There are 2 services that you need for a working site - a domain name and a web hosting plan for it. Whenever you type the domain name in your web browser, you see the content that’s uploaded in the web hosting account, but if that domain is not linked to such an account or to an email service, it is parked. To put it differently, the domain name is registered and you are its owner, but it doesn't have any content of its own. Instead, it can open either a pre-made “Under Construction / For Sale” page from the registrar company, or it can be directed to any other URL of your choice. The advantage of parking a domain is that you can keep it and be sure that no one else is going to take it. In the meantime, it's not going to block a slot for a hosted domain name within your account. In addition, you can park domains if you have a .com, for example, and you register domain names with other extensions such as .net, .org or country-code ones to forward them to the main site as a way to protect a brand name.