Depends on the audience; what do they expect to learn about computers or any OS
Try and pitch it to their level; if they aren`t that interested in the details of an OS, simplify it for them, you can always use analogies (to common shared ideas or objects)
https://wiki.debian.org/FilesystemHierarchyStandard
--for example, even though it would benefit people to understand FHS (File hierarchy Standard) or in the windows environment, the standard locations (can depend on the win version used, XP, win7, win8 etc) of files and perhaps the importance of organizing your data, many people will turn off
I guess their immediate question is WHY do I need to know, doesn`t the OS know what I want it to DO
--nope is the correct answer
You could also have a look at teacher guides
--they make be of some help,
http://www.thefreelibrary.com/'Teacher+Talking'+Computer+Guide+Series+Provides+Simplified+Approach...-a061958603
--the example below is lower grade and for MACIntosh, but could apply otherwise..
http://eric.ed.gov/?id=EJ438299
And the generic internet guides (wiki(s)) that are available to ALL
http://pdchandler.wikispaces.com/