It's very easy to forget how much jargon, let alone knowledge, you accumulate when you work in the business of science. I have given many lectures to lay audiences. It's an experience I actually always enjoy. It's a different kind of challenge, because you need to figure out a way to say what you want to say without using nitty-gritty details, and also without using words that are field specific--things that are second nature to you but have never been heard by some members of the public. To give one example, I gave a talk to a group of American Heart Association employees three weeks ago (ah, three weeks ago seems so distant now!). I talked about some drug discovery work I do in stroke, and how the AHA is supportive in certain unique ways, etc, etc. At the end, when I asked if anyone had any questions, someone raised their hand and asked, "What does NIH mean?"
If you want a good analogy for the level on which people need to be talked to, just watch any (literally any) commercial advertising a drug. That pain medicine works by making flashing streaks in your arms turn not flashy anymore! And that antibiotic makes microbes implode and disappear!
The trick is to talk to people in a way that's simplified but not essentially wrong. There are many layers of understanding to any problem, so you have to find the one that your audience is going to most connect with, no matter whether your audience is scientists in your field, out of your field, lay educated adults, high school students, little kids, or the president. If you really understand what it is you're saying and you really respect your audience, you will find a way to connect. That's been my experience.