There are two services that you need for a working web site - a domain and a web hosting plan for it. Each time you type the domain name in your Internet browser, you see the content that is uploaded within the web hosting account, but if that domain address isn't linked to such an account or to an email service, it's parked. To put it differently, the domain address is registered and you're its owner, but it lacks content of its own. Rather, it can open either a pre-made “Under Construction / For Sale” webpage from the registrar company, or it could be forwarded to some other URL of your choice. The main benefit of parking a domain address is that you can keep it and make sure that nobody else is going to take it. Meanwhile, it won't occupy a slot for a hosted domain in your account. You could also park domains if you have a .com, for instance, and you register domain names with other extensions such as .net, .org or country-code ones to direct them to the main site as a way to protect a brand name.