The hosted domains feature of a website hosting account refers to the number of registered domain names which you could add in the same account. Registering a domain address and hosting it are two completely different services although some people consider them to be the same thing. While the registration means that you become the owner of a specific domain name, the hosting part is what actually allows you to have a website as this is where your files and emails are going to be. Because these are 2 different services, you can register a new domain address with one company and host it with another one by modifying its name servers (DNS) - the domain shall work in the exact same way just as if it was registered and hosted with the exact same company. Also, it is very important to know that changing the hosting means directing the domain name to a different company and not transferring it.