The hosted domains feature of a web hosting account refers to the amount of registered domains that one can add within the exact same account. Registering a domain and hosting it are 2 completely different services although a lot of people consider them to be the same thing. While the registration means that you become the owner of a given domain name, the hosting part is what in fact enables you to have a website considering that this is where your data and emails will be. Since these are 2 independent 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 is going to work in the exact same way just as if it was registered and hosted with the same company. It's also very important to know that changing the hosting means directing the domain address to a different company and not transferring it.