What is the difference between pelicanconf and publishconf when using Pelican

I used the pelican-quickstart to create a static website and this comes with a default pelicanconf and publishconf. I have a GOOGLE_ANALYTICS variable in my publishconf, but when I publish my static page in Github Pages, using this snippet:

<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', '{{ GOOGLE_ANALYTICS }}']);
_gaq.push(['_trackPageview']);

(function() {
  var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
  ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') +   '.google-analytics.com/ga.js';
  var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>

, _setAccount becomes empty string.

Should I move GOOGLE_ANALYTICS from publishconf to pelicanconf? What's the difference between them?