The "seater width" on a sofa refers to the width of the seating area or the space
available for one person to sit on. It is the measurement of the cushioned or seating
portion of the sofa, being one section.
The "number of seats" on a sofa refers to the count of individual seating spaces with
or without cushions on the sofa.
The "sofa width" refers to the measurement of the sofa from one outer edge to the
other. It represents the overall width of the entire piece of furniture, including the
width of the arms.
Chair foam filling refers to whether the chair has a back seat made of fabrics, or not.