A subdomain (or subdomain; English: Subdomain) is a domain belonging to a higher domain in the domain name system hierarchy. For example, mail.example.com and calendar.example.com are two subdomains of example.com, and example.com is a subdomain of the top-level domain.com.
WWW2 is the subdomain name of the shunt server in the World Wide Web. It is mainly used to identify some related websites within a domain name. www.example.org, www2.example.org, and www3.example.org are examples of them. These subdomains can be extended to WWW3, WWW4, WWW5, WWW6, etc., and so on. Generally speaking, these domain names are used for server load balancing. Sometimes, even when browsing the website mirroring, these special domain names will be hidden, and the display will still be "WWW".
Domain Name System