Revit Architecture
Revit MEP
A room is a subdivision of space within a building model, based on elements such as walls, floors, roofs, and ceilings. These elements are defined as room-bounding. Revit refers to these room-bounding elements when computing the perimeter, area, and volume of a room.

In Revit, you can turn on/off the Room Bounding parameter of many elements. You can also use room separation lines to further subdivide space where no room-bounding elements exist. When you add, move, or delete room-bounding elements, the room’s dimensions update automatically.
An area is a subdivision of space within a building model, typically on a larger scale than individual rooms. However, areas are not necessarily bounded by model elements. You can draw area boundaries or pick model elements to use as boundaries.
When you add model elements, the area boundaries do not necessarily change automatically. You can specify how area boundaries behave: