A domain name is the unique .com (or dot whatever) address where your site can be found on the web. But in order to get your website online, you'll also need a web host to provide the server space necessary to store your site. For a fully-functional site, you need both a domain name and a good web host. Like peanut butter and jelly, they're better together. To make things simple, you can keep your needs in-house, letting one provider supply both your domain name and web hosting needs.