A web server is a computer system that processes requests via HTTP, the basic network protocol used to distribute information on the World Wide Web. The term can refer to the entire system, or specifically to the software that accepts and supervises the HTTP requests
Apache Tomcat, often referred to as Tomcat Server, is an open-source Java Servlet Container developed by the Apache Software Foundation (ASF). Tomcat implements several Java EE specifications including Java Servlet, JavaServer Pages (JSP), Java EL, and WebSocket, and provides a “pure Java” HTTP web server environment in which Java code can run.
Tomcat is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation, released under the Apache License 2.0 license, and is open-source software.
JBoss Web Server is an enterprise ready web server designed for medium and large applications, based on Tomcat
JBoss Web Server provides organizations with a single deployment platform for Java Server Pages (JSP) and Java Servlet technologies, PHP, and CGI.
JBoss Web Server can be used as a high performance generic web server instead of common native web servers like Apache Httpd or IIS.
JBoss Web Server is based on Apache Tomcat that is used in the official Reference Implementation or the Java Servlet and JavaServer Pages technologies.
JBoss Web Server uses Apache Portable Runtime that gives platform independance and modern OS technologies like sendfile support that lowers the CPU usage and thus offers the higher permomance/cost ratio. Apache HTTP Server itself uses Apache Portable Runtime.