|Many Web addresses begin with www, because of the long-standing practice of naming Internet hosts (servers) according to the services they provide. So, the host name for a web server is often www as it is ftp for an FTP server, and news or nntp for a USENET news server etc. These host names then appear as DNS subdomain names, as in “www.example.com”.
The use of such subdomain names is not required by any technical or policy standard; indeed, the first ever web server was called “nxoc01.cern.ch”, and many web sites exist without a www subdomain prefix, or with some other prefix such as “www2”, “secure” etc. These subdomain prefixes have no consequence; they are simply chosen names. Many web servers are set up such that both the domain by itself (e.g., example.com) and the www subdomain (e.g., www.example.com) refer to the same site, others require one form or the other, or they may map to different web sites.