If you'd like to register a domain to make sure that nobody else is going to take it, but you have not developed the site for it yet, you can park it. It's a service that registrar companies offer whenever a domain is not linked to any web or e mail hosting service. That way, you are able to protect a brand name, for example, and you'll own the domain name in question even though it will not open any content. If you want, you can choose some default template that the registrar provides, like For Sale or Under Construction, or you can forward the domain name to an alternative web address. Your second option is very helpful in case you own a number of domain names, but you want all of them to open the same site. As an example, you can register domain.net and domain.org, then park them and direct them to domain.com. In this example, you're going to need hosting for the third domain only and the traffic to the other ones will be redirected to it.