Short answers, pulled from the story.
A room is any enclosed space within a building or a ship, typically bounded by walls and reachable only through a door or other dividing structure. Its entrance connects it to a passageway, another room, or the outdoors, and it is usually large enough for several people to move about. Rooms also appear in structures like trains.
The use of rooms dates at least to early Minoan culture around 2200 BC. Excavations at Akrotiri on Santorini reveal clearly defined rooms, including rooms built above others and joined by staircases, plus bathrooms with alabaster washbasins, bathing tubs, and toilets served by twin ceramic plumbing for cold and hot water.
Homes contain work rooms such as kitchens, pantries, root cellars, home offices, sewing rooms, and laundry rooms, along with toilets and bathrooms for comfort and cleanliness. They also include social rooms like the great hall, drawing room, sitting room, living room, or parlour, and sleeping rooms such as bedrooms, guest rooms, nurseries, and box rooms.
In the 17th, 18th, and 19th centuries, those who could afford it kept these facilities apart from the main house. The kitchen was detached or placed in the basement to reduce fire risk and keep heat and cooking smells away during warm months, while the toilet, often a simple pit latrine, was set in an outhouse or privy to keep smell and insects at a distance.
A box-room is a small room found in many United Kingdom houses, easily identified because it is smaller than the others. Its small size limits its use to a small single bedroom, a small child's bedroom, storage, or housing for a live-in domestic worker, though traditionally up until the 1930s it stored boxes, trunks, and portmanteaux.
An en-suite room is a type of room that includes a private room, a private washroom, and access to a communal kitchen, with the washroom generally holding an en-suite shower, a sink, and a toilet. In student accommodation, en-suite usually indicates a private space intended to provide study room and a peaceful environment.