If you wish to register a domain name to make sure that nobody else is going to take it, however, you have not built the website for it yet, you could park it. That is a feature that registrar companies offer whenever a domain name is not linked to any web or email hosting service. That way, you'll be able to protect a brand name, for instance, and you'll own the domain in question although it won't open any content. If you want, you can select some default template that the registrar offers, like For Sale or Under Construction, or you can direct the domain name to a different web address. Your second option is very useful in case you own a few domain names, but you want all of them to open the same website. For instance, you may register domain.net and domain.org, then park them and forward them to domain.com. In this example, you'll need hosting for the third domain only and the traffic to the other ones is going to be redirected to it.