Tomcat is the Java Servlet / Java Server Page environment produced
by the Apache Foundation's Jakarta Project.  Tomcat can be run as a
standalone web server with Servlet and JSP support, or using Apache
Server as its web server via the mod_jk Apache module (the
www/ap-jk package).

mod_jk is a replacement to the elderly mod_jserv. It is a completely
new Tomcat-Apache plugin that handles the communication between
Tomcat and Apache

Homepage:
https://tomcat.apache.org/connectors-doc/
