1.2. A is...

• Apache. (The most common web-server on the Internet. Highly configurable and extensible.)
• AOLserver. (A Tcl-enabled feature-rich web-server created by America On-Line).
• thttpd (Tiny/Turbo/Throttling HTTP Server)
• Roxen

And even:

• Perl's HTTP::Daemon and friends in other languages.
• TUX (a web-server in the kernel)
• Microsoft's IIS.