The hosted domains feature of a web hosting account indicates the amount of registered domains that you could include within the same account. Registering a domain and hosting it are 2 completely different services although many people consider them to be the same thing. While the registration signifies that you become the owner of a given domain address, the hosting aspect is what really allows you to have a website since this is where your files and emails are going to be. As these are two separate services, you can register a new domain name with one company and host it with another one by changing its name servers (DNS) - the domain name is going to work in the exact same way as if it was registered and hosted using the same company. It is also very important to know that changing the hosting means directing the domain name to another company and not transferring it.