The hosted domains feature of a web hosting account refers to the amount of registered domain names that you could include in the exact same account. Registering a domain name and hosting it are 2 totally different services although a lot of people consider them to be the exact same thing. While the registration ensures that you become the owner of a given domain, the hosting part is what really enables you to have a site because this is where your data and e-mails are going to be. Since these are 2 independent services, you can register a new domain address with one company and host it with another one by changing its name servers (DNS) - the domain address shall work in the exact same way just as if it was registered and hosted with the exact same company. It is also important to know that changing the hosting means pointing the domain address to a different company and not transferring it.