What's the difference between JRuby Jars

I haven’t been able to find any place that explains the difference
between the various JRuby jars.

There seems to be at least 4 -
– jruby.jar that is part or the normal JRuby installation
– jruby-complete
– jruby-core
– jruby-stdlib

Perhaps one of the Forum members knows where I can find the info?

Inevitably this leads me to wonder what is the purpose of the different
versions? Why not use the jruby-complete everywhere (if it is what it
claims to be)?