When it comes to teaching people how to fight, I for one have a pretty limited technical knowledge base, and my time and interest level keeps me from expanding on that too drastically.
When I'm teaching someone to fight, I'm doing it in "layman's terms" because that's quite simply how I know it. I've read loads of books, etc, on the subject, and have some basic ideas of what I'm trying to do/replicate, but I'll admit I'm far from an expert.
Mainly, when I'm teaching I'm very quick to recognize weaknesses/mistakes that I can capitolize on. Most of my training has to do with pointing those mistakes out to my "student" and describing/showing/teaching "better" methods that will eliminate or at least limit things that I would capitolize on in a fight. I'm essentially teaching my student's (or attempting to teach) to beat me.
When a student reaches a point where they're equal to me, or exceed my abilities, I'm "out of ideas" for the most part, and can't teach them much beyond that...
Fortunately (for my ego?) I haven't had that happen all that much- but I'll be the first to admit I'm not "expert" quality...