What is the meaning of central message?

Central idea in a particular play or novel or poem many not be the same as someone else's but that is part of the enjoyment of literary discussion and argument.

"The central-passage house, also known variously as center-hall house, hall-passage-parlor house, Williamsburg cottage, and Tidewater-type cottage, was a vernacular, or folk form, house type from the colonial period onward into the 19th century in the United States."