A parked domain address is one that is taken, yet it is not linked to another service - web or email hosting. To put it differently, this kind of domain name will not open any real content if you type it inside a web browser, but no one else can take it as you've already registered it and you are its owner. The advantage of acquiring a domain name and parking it afterwards is that you will be able to keep it and not stress that someone else might register it in the meantime if, for example, the website for it is not ready yet. You could set a short-term Under Construction page for a parked domain while you're working on your web site, or direct it to another web address - temporarily or permanently. The second option can be employed when you have already registered domain.com, for example, and you obtain domain.net and domain.org, so that you can protect a brand name or a trademark. In this case, the .net and .org domains can be parked and directed to the .com as you do not need different websites for them.