If you have a number of domains with different extensions and you would like all of them to open exactly the same site, you can have the site under one of them and forward the others. There are several ways to forward one domain to another, among them the so-called domain parking. When your web hosting plan allows it, though, it will be better if you host all of the domains and set up a URL redirect, not a domain redirect. The real difference between the two is that while a domain address is hosted, you could still have content for it, set up subdomains, e mail addresses, and so on., while with a parked domain you cannot do any of these things. For example, if you're building localized sites under various country-code domain names, you'll be able to work on them, but in the meantime, visitors will be forwarded to the main website.