A domain name is a name used to identify a website on the internet. Beneath the surface, websites are associated with IP addresses. These are basically numerical addresses that tell your browser where to find the website on the internet. To make things simpler for humans every website has a corresponding name. You can think of domain name as the human readable version of the IP address.
An example of a domain name would be: wpbeginner.com
They can be purchased through an online registrar such as Godaddy or one of the many domain name resellers. ICANN (the Internet Corporation For Assigned Names And Numbers) authorizes these registrars to sell domain names.
Many WordPress hosting providers such as Bluehost will provide one free domain registration with their packages. You can change the domain name location from one web host to another by changing its DNS settings. DNS settings basically tell the DNS servers which IP address corresponds to that domain name. When you change hosts, your IP address will change because you are changing servers.
There are many different domain name extensions that are available. Some of the most popular domain name extensions are: .com, .net, .org, .info, .edu, .biz. There numerous other country level domains such as .us, .in, .ly, .io, and many more.