I've always heard that used to refer to a house with a central hallway from the front door to the back door, with all the rooms on either side.
No, not necessarily.
That's one variation.
Apparently the earliest version had rooms stacked next to each other with adjoining doors and no hall way.
All the doors, and the front and back doors, would line up.
OK, here's an illustration of this type with a couple of variations.
More elaborate versions (often in the South and associated with New Orleans, had a central hallway with rooms arranged to either side, and sometimes with a parlor across the front of the house and a kitchen or dining room across the rear of the house.
Floor furnaces were popular in the central hall shotgun house because you could get heat to the entire house without needing ductwork.
