(World Wide Web) The common host name for a Web server. The "www-dot" prefix on Web addresses is widely used to provide a recognizable way of identifying a Web site. Computers read Web addresses (URLs) from right to left, so that the WWW is the last component of the address.

WWW Is Optional
Today, the WWW prefix is mostly optional, and it is common to advertise only the domain name such as computerlanguage.com without the WWW. Web sites are typically configured to default to a WWW Web server if only the domain name is used. Try it. Type the name of a Web site into your browser using only the domain name, such as computerlanguage.com. See dub-dub-dub, World Wide Web, DNS and URL.

WWW2, WWW3, etc.
Organizations use WWW2, WWW3 and other similar prefixes as a way of identifying additional Web sites or Web content. This is strictly an arbitrary naming that differentiates their own sites from the ones that use the WWW prefix, which has become a default. The names have no connection to "Internet 2" or other global systems or standards.