The difference between jQuery, jQuery UI, and Plugins...

The difference between jQuery, jQuery UI, and Plugins...


Hello,
I have looked, but could not find a good explanation that tells the
difference between jQuery, jQuery UI, and Plugins. What is the
difference between them? I experimented with jQuery months ago, and
don't remember seeing a UI version in the tutorials, is it new?
Lastly, is jQuery UI licensed the same way as the original jQuery?
I'm sorry if this has been covered elsewhere, but I didn't see any
information in the FAQ or in the support groups.
Thanks!