The term 'beam supporting floorboards' can be summarized as a JOIST, which is a structural element that provides support for floors and ceilings. Joists are typically made of wood, metal, or concrete and are laid in a parallel series across the length of a room. They are connected to beams, which provide additional support and stability to the structure. Joists are essential for providing a strong foundation for floorboards, which are then laid on top of them.