In case you have a few domain names with different extensions and you need all of them to open precisely the same website, you could have the site under one of them and forward the others. There are a number of approaches to forward one domain name to another, such as the so-called domain parking. If your website hosting package allows it, though, it will be better if you host each of the domains and set up a URL redirect, not a domain redirect. The primary 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 many others., while with a parked domain you can't do any of these things. As an example, if you're building localized websites under different country-code Internet domain names, you will be able to work on them, but meanwhile, people shall be redirected to the main site.