When you have a few domains with different extensions and you would like all of them to open exactly the same site, you could have the Internet site under one of them and forward the others. There are various approaches to redirect one domain name to another, like the so-called domain parking. If your hosting plan allows it, though, it'll be better if you host each of the domains and create a URL redirect, not a domain redirect. The real difference between the two is that while a domain address is hosted, you can still have content for it, create subdomains, email addresses, etc., while with a parked domain you can't do any of those things. For example, if you are building localized websites under various country-code domains, you'll be able to work on them, but in the meantime, people shall be redirected to the primary website.