>You can explain what you do and why it's important in terms they understand, but it'll take so long they'll get bored and wish they hadn't asked.

Yes, don't fall into this trap. The other two options are still better. Everyone says, "no, no, I really want to know" and then tunes out two minutes later; then four minutes later they start doing the George Carlin lean: "Surgery! I am having my ears sewn shut!".