The hosted domains feature of a website hosting account indicates the amount of registered domains that one can include in the same account. Registering a domain and hosting it are 2 totally different services although a lot of people consider them to be the very same thing. While the registration means you become the owner of a specific domain address, the hosting aspect is what in fact allows you to have a website as this is where your data and emails are going to be. Because these are 2 independent services, it is possible to register a new domain address with one company and host it with another by changing its name servers (DNS) - the domain shall work in the exact same way as if it was registered and hosted using the same company. It's also very important to know that changing the hosting means pointing the domain name to an alternative company and not transferring it.