When you have several domains with different extensions and you need all of them to open the very same site, you can have the website under one of them and forward the rest. There are various ways to redirect one domain name to another, including the so-called domain parking. If your website hosting plan allows it, though, it shall be better if you host all of the domains and create a URL redirect, not a domain redirect. The main difference between the two is that while a domain is hosted, you may still have content for it, set up subdomains, e mail addresses, and so on., while with a parked domain you are unable to do any of those things. For example, if you are building localized Internet sites under various country-code domains, you shall be able to work on them, but meanwhile, visitors shall be redirected to the primary Internet site.