There are two services that you need for a functioning site - a domain name plus a hosting plan for it. If you type the Internet domain in your web browser, you see the content that’s uploaded within the web hosting account, but if that domain address is not linked to such an account or to an e-mail service, it's parked. Put simply, the domain address is registered and you are its owner, but it does not have any content of its own. Instead, it can open either a pre-made “Under Construction / For Sale” Internet page from the registrar company, or it can be directed to some other URL of your choice. The main benefit of parking a domain is that you can keep it and be sure that nobody else is going to take it. Meanwhile, it's not going to block a slot for a hosted domain name within your account. You could also park domains if you have a .com, for example, and you register domain addresses with other extensions like .net, .org or country-code ones to direct them to the main site in order to protect a brand name.