A layman is someone who doesn't have specialized training or expert knowledge in a particular field. When doctors explain medical procedures in layman's terms, they're translating complex ideas into everyday language that ordinary people can understand. A layman might know that the heart pumps blood, but a cardiologist understands the intricate details of how each valve and chamber works.

The word doesn't mean someone is unintelligent or uneducated overall. A brilliant mathematician might be a complete layman when it comes to car engines, just as an expert mechanic might be a layman regarding advanced mathematics. We're all laymen in most subjects because nobody can be an expert at everything.

Today, layman applies to any field. When a scientist writes for laypeople, she avoids technical jargon. When a lawyer explains a case to a lay jury, he uses clear language instead of legal terminology. Being a layman simply means you're on the outside looking in on someone else's area of expertise, and there's nothing wrong with that. It describes most of us most of the time.