In case you have a lot of domains with different extensions and you want all of them to open the exact same site, you may have the site under one of them and forward the others. There are a number of methods to redirect one domain to another, such as the so-called domain parking. If your hosting package deal allows it, though, it will be better if you host all of the domains and create a URL redirect, not a domain redirect. The main difference between the two is that while a domain name is hosted, you may still have content for it, set up subdomains, e mail addresses, and so forth., while with a parked domain it's not possible to do any of these things. As an example, if you are building localized sites under various country-code domain names, you'll be able to work on them, but meanwhile, people will be redirected to the primary website.