When you have a few domains with different extensions and you need all of them to open the exact same site, you may have the website under one of them and redirect all the rest. There are several approaches to forward one domain name to another, including the so-called domain parking. When your hosting package allows it, though, it shall be better if you host all of the domains and create a URL redirect, not a domain redirect. The real difference between the two is that while a domain is hosted, you could still have content for it, create subdomains, email addresses, and so on., while with a parked domain you cannot do any of these things. As an example, if you are building localized websites under several country-code domain names, you shall be able to work on them, but at the same time, people will be forwarded to the primary site.