The hosted domains feature of a website hosting account denotes the amount of registered domains which you could add in the same account. Registering a domain name and hosting it are 2 different services although many people consider them to be the same thing. While the registration means that you become the owner of a certain domain, the hosting aspect is what in fact enables you to have a site considering that this is where your data and emails will be. As these are two separate services, you are able to register a new domain with one company and host it with another one by changing its name servers (DNS) - the domain is going to work in the exact same way as if it was registered and hosted with the same company. It is also important to know that changing the hosting means directing the domain to a different company and not transferring it.