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: thepurpleteacup.com
Source: WPBeginner – for more information on Domains, click here