Email addresses are used as identifiers for email accounts on servers. It is used to direct and deliver, as well as receive, emails to the proper email servers. While many businesses and professionals have their own email servers and domains, most simply use email services like Gmail and Outlook, and therefore, use domains such as gmail.com and outlook.com.
Email addresses consists of two elements. The username and domain name. Like URLs, email address domains reflect the IP address the DNS server points it to. Also like URLs, they support subdomains and a wide range of TLDs.