Registering a domain name and hosting one is commonly mistaken by a lot of people to be one and the same thing. These are in fact 2 different services - the domain registration is the actual name and nothing else, while the hosted domains feature reveals the amount of already registered domains that you can accommodate in the same hosting account and have website files and email messages for them. Your websites will function in precisely the same way no matter if the domain addresses are registered and hosted at the same place or are registered with company A and directed to company B. Simply registering a domain address without hosting it will give you ownership, but will not allow you to have a web site if you don't host this domain in some account so that records for it are set up and it starts opening the information from that account.
