The hosted domains feature of a website hosting account refers to the amount of registered domains that one can include in the exact same account. Registering a domain address and hosting it are two totally different services even though many people consider them to be the same thing. While the registration ensures that you become the owner of a given domain name, the hosting part is what really permits you to have a site because this is where your data and emails are going to be. As these are 2 different services, it is possible to register a new domain with one company and host it with another by modifying its name servers (DNS) - the domain name will work in the exact same way just as if it was registered and hosted with the same company. It's also extremely important to know that changing the hosting means pointing the domain name to another company and not transferring it.