If they don't have the basic tools for comprehension then how do you explain it to them?
You start with analogies to what you have in common. You seek out a mutual frame of reference, and then you start with the fundamentals, explaining as you go, until they have the necessary framework to fully understand the idea.
It's a process called "teaching". Since you can read and write I assume that you've experienced this process sometime in the past.
(BTW IQ isn't a measurement of innate brain ability. It's a measure of educational success. I point this out whenever possible because it's a common misunderstanding of what IQ means.)
[This message has been edited by crashfrog, 11-02-2003]