In case you have a number of domains with different extensions and you want all of them to open the same website, you could have the site under one of them and forward the others. There are a number of approaches to redirect one domain to another, such as the so-called domain parking. When your web hosting package allows it, though, it will be better if you host each of the domains and set up a URL redirect, not a domain redirect. The main difference between the two is that while a domain address is hosted, you may 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. For example, if you're building localized websites under various country-code domains, you shall be able to work on them, but in the meantime, people will be forwarded to the main website.