A parked domain address is one that is taken, however it's not associated with another service - web or email hosting. Basically, such a domain will not open any real content when you type it inside a web browser, but nobody can take it as you've already registered it and you are its owner. The benefit of acquiring a domain and parking it afterwards is the fact that you’re able to keep it and not worry that somebody else may register it in the meantime if, for example, the website for it is not ready yet. You may set a short-term Under Construction website page for a parked domain address while you're working on your site, or direct it to some other web address - temporarily or permanently. The latter option can be used when you have already registered domain.com, for example, and you acquire domain.net and domain.org, so as to protect a brand name or a trademark. In such a case, the .net and .org domain addresses can be parked and directed to the .com because you don't need different websites for them.