I have to teach (force feed) my superiors something about what I'm doing every day. They have no clue, nor are they really interested.
The good thing is that you have a chance to teach him/her some appreciation for what you do.
S/He's got you to do the hydraulics stuff, so just ask him/her first how much s/he really want's to learn about it. According to my experience, it's probably not going to be a lengthy assignment. I imagine s/he'll be happy with as brief as possible.