The hosted domains feature of a hosting account indicates the number of registered domains that you could add within the same account. Registering a domain name and hosting it are two completely different services although some people consider them to be the exact same thing. While the registration means you become the owner of a certain domain name, the hosting aspect is what in fact allows you to have a site as this is where your files and emails will be. Because these are 2 independent services, you'll be able to register a new domain with one company and host it with another one by changing its name servers (DNS) - the domain name shall work in the exact same way as if it was registered and hosted with the same company. It's also extremely important to know that changing the hosting means directing the domain address to another company and not transferring it.