A parked domain is one that is taken, but it's not associated with some other service - web or email hosting. Put simply, this kind of domain address won't load any real content if you type it within a web browser, but nobody else can take it as you've already registered it and you are its owner. The benefit of acquiring a domain name and parking it afterwards is the fact that you are able to keep it and not stress that somebody else may register it in the meantime if, for example, the site for it is not ready yet. You can set a temporary Under Construction page for a parked domain address while you are working on the website, or direct it to another web address - temporarily or permanently. The latter option can be used if you have already registered domain.com, for example, and you get domain.net and domain.org, so as to protect a brand name or a trademark. In this situation, the .net and .org domain addresses can be parked and directed to the .com since you do not need different sites for them.