If you wish to register a domain to make sure that no one else is going to take it, however, you have not developed the web site for it yet, you may park it. It's a feature that registrar companies provide whenever a domain is not linked to any web or email hosting service. This way, you can protect a brand name, for instance, and you will own the domain name in question although it will not load any content. If you wish, you can pick some default template that the registrar offers, like For Sale or Under Construction, or you can direct the domain to an alternative web address. The second option is very helpful if you own a number of domains, but you want every one of them to open the same website. As an example, you could register domain.net and domain.org, then park them and forward them to domain.com. In this example, you're going to need hosting for the third domain name only and the traffic to the other ones will be redirected to it.