Strictly speaking, one domain name is all you need to host a website. However, having just one may not be a good idea. Consider the following scenario. Your business is called Acme Widgets and therefore you want to register the domain name acme.com. When you try to obtain the domain name, you discover that someone else has already registered it. That's disappointing, but you decide to try again, this time with widgets.com. Oops, that one is taken also. After many attempts at finding a domain name you like, you discover that acmewidgets.com is available and you grab it before someone else can.

So now you have a domain name that you like, but what if someone else (a competitor perhaps) registers acmewidgets.net and acmewidgets.org and points these names to their web site? That is not good since your customers could easily mistake which domain name belongs to you. They could end up at your competitors web site when trying to reach yours!

Domain names cost less than $10 per year to register. At this price, you can't afford not to register variations on your domain name and point them all to your website. This is a cheap way to guard your company identity.