As Wrzlprmft pointed out, you don't want to tell the audience things they don't understand. But sometimes that's the only audience you got and you have to make it work. Besides, this quote will keep bugging you if you give up:
If you can't explain it to a six year old, you don't understand it
― Albert Einstein
I would start with a heuristic. Compare it to something they do understand, something simple that everyone knows. For instance, when they explain software engineering, they often compare it to constructions of houses.
Some visual examples help. Yesterday I had to explain "statistical significance" to a friend of mine who has no idea about statistics. I flipped a coin, got heads and said that his coin had a 100% chance of rolling heads. He replied "Bull****!". I flipped it two more times and got heads and tails. I told him now it looked like it had a 67% chance of heads. He looked at me suspiciously. Then I said if I flipped it about 100 times, it would come to about 50% chance of heads, which is close to the truth. He got it after that presentation, even though I never even gave him a definition of "statistical significance". Inserting an easy-to-understand picture into the PowerPoint also does the trick.
Replace the technical lingo with common words whenever possible.
Also, trying to cover multiple difficult topics rarely works in any presentation. I usually pick the most important point and focus on it. If it is too broad, go a level higher. Zoom out and lose the details. Or pick a subtopic and dedicate your presentation to it. That's the trade-off you got to make.
But the most important thing is to do it. Practice, make mistakes, correct them, and improve. By the time someone wins a Nobel Prize, they are always able to explain their work to general public in a few minutes.