When a webapp is loaded, $CATALINAHOME/conf/web.xml is parsed, then <APPHOME>/WEB-INF.xml. The shared version of web.xml should contain directives for all webapps.
$CATALINA_HOME hold the path to the root of the Tomcat installation
Tomcat can either be installed as a service, or can be run as a daemon. It should always be run using the startup script in bin/
Users are configured using conf/tomcat-user.xml