I really like the paint analogy on Wikipedia for explaining this concept to laypeople who will never need to understand how DH actually works.
If you need to explain DH to someone who demands an understanding of what it actually does, DH is so easy that you might as well have them bang it out with small numbers in their scripting language of choice; you can talk someone though DH in about 4 minutes, and it even works as a sort of magic trick if there's a third person in the room who can hear your public values (again: use 2-3 digit numbers).
If you need to explain DH to someone who demands an understanding of what it actually does, DH is so easy that you might as well have them bang it out with small numbers in their scripting language of choice; you can talk someone though DH in about 4 minutes, and it even works as a sort of magic trick if there's a third person in the room who can hear your public values (again: use 2-3 digit numbers).