[Zope] "proxy roles", search engine for documentation.

Hi, Can someone give a 1-para description of proxy roles? The ZMG mentions them, but not what they are, or do. My guess is that it's like a Unix setuid program - anyone viewing the document gets the changed permissions, for the purpose of loading other objects into that object... On a related note - could a search engine be added to the Zope Documentation area of the site? Please? :) Anthony