In order to make a web site, you need 2 things - a domain and a web hosting plan for it. The domain registration is the actual web address that you type in a web browser to reach a site, while the hosting space is where your site files will be. These are 2 tightly connected, but separate services, while many people assume that registering the domain is enough. Similar to the disk space and the monthly traffic features that a given web hosting plan provides, there are a certain number of registered domain names that you can add as hosted i.e. you can have the web content for them in some account even when the domains are actually registered through a different provider. In technical terms, it doesn't matter whether a domain is registered and hosted with the same company or is registered with one company and directed to another - either way your sites will function exactly the same way.