A domain, or domain name, is your website address. Just like your physical address, it’s just an address on the internet that specifies where your browser should go to look for information. Some people confuse their domain with their website.
Think of the domain as your home address. It’s an easy way for people to find your house. Then think of your website as the house itself, contents and all. The domain is just a simple way for people to be able to find you.
When you register a domain name on the internet (and pay the registration fees), you are buying the right to use that domain name for a year (or whatever term is specified).