A lot of people get confused when the subject of websites and domain names comes up. A common belief is that a domain name is irrevocably bound to a website - this is not the case. But let me start with the basics.
According to the Collins English Dictionary, a website is “a group of connected pages on the World Wide Web containing information on a particular subject.” The same source defines a domain name as “a unique name, corresponding to one or more numeric IP addresses, used to identify a particular web page or set of web pages on the internet.”
So, your website is a collection of pages with information - your home page, your “about us” page, your “contact us” page and so on. Your domain name is the address for your website - www.acmecorp.com, for instance. You need both to have a presence on the internet.
The whole thing is similar to having a mobile phone. Your website is equivalent to your handset, and your domain name is similar to your SIM card. Having a handset is all very fine, and, of course, necessary, but you can’t make or receive calls unless you also have a SIM card that provides you with a phone number.
But here’s what’s interesting: You don’t have to get your SIM card from the same people you got your handset from. You can use any SIM card in any handset (leaving aside issues like unlocking and SIM card sizes.) Let’s face it - you wouldn’t cancel your contract just because you wanted a new handset, would you?
It’s exactly the same situation with an internet presence. I have a website, a set of web pages, hosted with company x. I own a domain name, www.creativecats.com, registered with company y. I can point that domain name at any website I wish. If I decided that I wanted to move my website to be hosted by company z, I could do that. I can even point it at a website that doesn’t belong to me, like my company’s Google+ page, or my Facebook page. Or even a page that has nothing whatsoever to do with me, like the weather channel. I wouldn’t do it because it makes no sense, and I have no idea if that sort of thing would be legal, but technically I could.
A domain name is just that - a name. Something people can type into their web browser to find whatever you want them to find at the end. It is not a website, it holds no content, and it’s not irrevocably fixed. It’s just a way for your customers to get through to the right person - just like your phone number.