If you have a few domain names with different extensions and you would like all of them to open exactly the same website, you could have the website under one of them and redirect the others. There are different approaches to forward one domain to another, like the so-called domain parking. When your web hosting plan permits it, though, it will be better if you host all of the domains and create a URL redirect, not a domain redirect. The difference between the two is that while a domain name is hosted, you may still have content for it, create subdomains, e-mail addresses, and so forth., while with a parked domain you can't do any of those things. For instance, if you are building localized sites under several country-code domain names, you'll be able to work on them, but at the same time, visitors shall be redirected to the primary Internet site.