A parked domain is one which is taken, but it's not linked to some other service - web or e mail hosting. Basically, such a domain address will not load any actual content if you type it inside a web browser, but nobody can take it as you've already registered it and you are its owner. The best thing about getting a domain and parking it afterwards is the fact that you will be able to keep it and not stress that someone else could possibly register it in the meantime if, for instance, the website for it is not ready yet. You can create a temporary Under Construction webpage for a parked domain while you are working on your site, or forward it to some other web address - temporarily or permanently. The latter option can be employed if you have already registered domain.com, for instance, and you acquire domain.net and domain.org, in order to protect a brand name or a trademark. In this situation, the .net and .org domain names can be parked and directed to the .com since you do not need different sites for them.