CATALINA_OPTS v JAVA_OPTS - What is the difference?

There are two environment variables - CATALINA_OPTS and JAVA_OPTS -
which are both used in the catalina.sh startup and shutdown
script for Tomcat. They are described in comments within that file as:

(optional) Java runtime options used when the "start", "stop" or
"run" command is executed [JAVA_OPTS]

and

(optional) Java runtime options used when the "start" or "run"
command is executed [CATALINA_OPTS]

So why are there two different variables? And what's the
difference?

Firstly, anything specified in EITHER variable is passed, identically,
to the command that starts up Tomcat - the "start" or "run" command -
but only values set in JAVA_OPTS are passed to the "stop" command. That
probably doesn't make any difference to how Tomcat runs in practise as
it only effects the end of a run, not the start.

The second difference is more subtle. Other applications may also use
JAVA_OPTS, but only Tomcat will use CATALINA_OPTS. So if you're setting
environment variables for use only by Tomcat, you'll be best advised to
use CATALINA_OPTS, whereas if you're setting environment variables to be
used by other java applications as well, such as by JBoss, you should
put your settings in JAVA_OPTS.