If you have a lot of domain names with different extensions and you want all of them to open the exact same site, you could have the site under one of them and redirect the others. There are several methods to redirect one domain name to another, among them the so-called domain parking. When your hosting package deal allows it, though, it'll be better if you host all of the domains and set up a URL redirect, not a domain redirect. The main difference between the two is that while a domain is hosted, you may still have content for it, set up subdomains, email addresses, and many others., while with a parked domain it's not possible to do any of those things. For example, if you are building localized sites under several country-code domain names, you will be able to work on them, but in the meantime, visitors will be redirected to the main website.