According to wikipedia:
A floor plan, or floorplan, in architecture and building engineering is a diagram, usually to scale, of the relationships between rooms, spaces and other physical features at one level of a structure.
Dimensions are usually drawn between the walls to specify room sizes and wall lengths. Floor plans will also include details of fixtures like sinks, water heaters, furnaces, etc. Floor plans will include notes to specify finishes, construction methods, or symbols for electrical items.
It is also called a "plan" in architectural terms, as opposed to "elevation" which means how the object will look when seen from a side, or a "cross section" where the building is shown cut along an axis to reveal the interior.