Layman

A layperson or layman is a person who is not an expert in a given field of knowledge. The term originally meant a member of the laity

Laity

In religious organizations, the laity comprises all people who are not in the clergy. A person who is a member of a religious order who is not ordained legitimate clergy is considered as a member of the laity, even though they are members of a religious order .In the past in Christian cultures, the...

, i.e. a non-clergymen, but over the centuries shifted in definition.

The concept of describing something in layman's terms has come into wide use in the English-speaking world. To put something in layman's terms is to describe a complex or technical issue using words and terms that the average individual (someone without professional training in the subject area) can understand, so that they may comprehend the issue to some degree.

Layman, 'laity': In short: "laity" means "common people". The English word "laity" comes from the Greek laikos which meant "of the people", "common" (common, in the meaning "unholy", "unclean" and similar). The related verb laikoô meant "to make common", "to desecrate".