A parked domain address is one that's taken, but it is not linked to some other service - web or e-mail hosting. Put simply, such a domain will not load any actual content when you type it in an Internet browser, but no one else can take it as you have already registered it and you are its owner. The advantage of acquiring a domain name and parking it afterwards is the fact that you are able to keep it and not stress that someone else may register it meanwhile if, for example, the site for it is not ready yet. You could set a temporary Under Construction page for a parked domain while you're working on your site, or forward it to another web address - temporarily or permanently. The second option can be used when you have already registered domain.com, for example, and you acquire 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 since you don't need different sites for them.