If you want to register a domain to make sure that nobody else will take it, however, you haven't built the web site for it yet, you can park it. That is a feature that registrar companies offer if a domain is not connected to any web or e mail hosting service. In this way, you'll be able to protect a brand name, for example, and you'll own the domain in question although it will not load any content. If you want, you can choose some default template that the registrar provides, like For Sale or Under Construction, you can also direct the domain to a different web address. Your second option is very helpful if you own a few domains, but you want all of them to open the same site. For example, you could register domain.net and domain.org, then park them and direct them to domain.com. In this example, you are going to need hosting for the third domain only and the traffic to the other ones is going to be redirected to it.