[Zope] REQUEST Variables and Caching

Can anyone here give me a quick explanation of how the 'REQUEST variables' field works in the RAM Cache Manager properties? I've looked and all I can find is: ---------------------------------------- This information is used to store the cached copy of a page. This is an advanced feature, for now, you can leave this set to just "AUTHENTICATED_USER". ---------------------------------------- I'm trying to ensure that the cache manager only caches things for users who are NOT logged in.