If you want to create a website, you need 2 things - a domain and a hosting plan for it. The domain registration is the actual web address which you type in a browser to reach a website, while the hosting space is where your website data will be. These are two tightly connected, yet separate services, even though many people believe that registering the domain name is enough. Similar to the disk space and the monthly traffic features which a given hosting plan features, there are a certain number of registered domains which you can include as hosted which means that you can have the web content for them in some account even when the domains are actually registered using a different company. In technical terms, it doesn't matter whether a domain is registered and hosted with the exact same company or is registered with one company and directed to another - in any case your sites will function exactly the same way.