Domain names put a friendly face on hard-to-remember numeric internet addresses. Every computer on the internet has a unique internet protocol (IP) number. A domain name represents one IP number or more. For example, the IP number for the domain name whitehouse.gov is 126.96.36.199. The whole purpose is to give users an easy-to-remember handle so that when sending an e-mail to, let's say, the President of the United States, you can type email@example.com instead of the more unwieldy firstname.lastname@example.org.
A domain name registration is simply reserving your website's name for a specified period of time. The two parties involved with a domain registration are generally the user who is registering the domain and the domain registrar. The domain registrant is the user who actually registers the domain name and the domain registrar is the company who helps that user with their domain registration.
Domain name registrars, in case you didn't know, are the companies that manage all the website domain names you'll see (EG: Inc.com) - the fingerprint of your business, which may also include the hosting and privacy measures. For example, by default many companies will actually over-price the simple process of keeping your registration information private (which if it isn't can be found via a simple Whois search).
Domain names can be used in a number of ways. Direct visitors to your website’s home page or use complementary domains to send them to specific areas of your website ( e.g. yourcompany.jobs for a careers page). Or, forward a custom domain to an existing social media account, like your Twitter profile or Periscope channel. With a domain name you can even set up custom email addresses like email@example.com, which can be used to conduct business or communicate with your followers. More.