In case you have a few domains with different extensions and you need all of them to open the very same website, you could have the Internet site under one of them and forward the others. There are various ways to redirect one domain name to another, among them the so-called domain parking. If your web hosting package deal allows it, though, it shall be better if you host all the domains and set up a URL redirect, not a domain redirect. The main difference between the two is that while a domain name is hosted, you could still have content for it, set up subdomains, email addresses, and so on., while with a parked domain it's not possible to do any of those things. As an example, if you are building localized sites under various country-code domains, you shall be able to work on them, but in the meantime, visitors shall be redirected to the main website.