When you have several domain names with different extensions and you need all of them to open exactly the same site, you can have the site under one of them and forward the rest. There are various methods to forward one domain name to another, like the so-called domain parking. When your website hosting package deal allows it, though, it'll 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 can still have content for it, create subdomains, e-mail addresses, and so forth., while with a parked domain it's not possible to do any of these things. As an illustration, if you are building localized sites under different country-code domain names, you will be able to work on them, but at the same time, people shall be redirected to the primary website.