Every website should have only one domain name by which it’s known, but there are few reasons to have multiple domain names pointing to that site. And they are as follows:
Common misspellings and variations
Suppose that your name is N2thenight; it would make sense to get an additional domain name with the spelling of Intothenight because most people will enter it that way out of habit.
Doing business in multiple countries
A British company might have a domain with the country’s top-level domain extension .uk, but also have the domain name with the .com extension. Keep in mind that most country domain regulators require a legal presence to register their domains.
Block competing domains
Someone else might register the same domain with a different extension. You can prevent this by registering the .com, .net, and .org versions of your domain name.
Special promotional domain names
Suppose that you develop an insurance quote calculator on your insurance website. It might be worth registering a domain such as insurancequote.com and point it at that page on your site.
Although most new domain names are not expensive, having a lot of domain names can add up, so you’ll need to weigh how important some of these variations are: How likely misspellings might be, how much competition there is, and whether people in certain country’s care if they’re going to a domain with another country’s domain extension.
It’s best to keep an eye out for which top-level domain (TLD) extensions are actually being used (how many .info domains you see, for example, after being available for several years now). Or if the price isn’t much more than a regular domain, it might be worth registering on a year-by-year basis to see where the extension goes.