A window with sashes that slide vertically and allow opening from the top and bottom.
double-hung window (Wikipedia)
A sash window or hung sash window is made of one or more movable panels, or "sashes", that form a frame to hold panes of glass, which are often separated from other panes (or "lights") by glazing bars, also known as muntins in the US (moulded strips of wood). Although any window with this style of glazing is technically a sash, the term is used almost exclusively to refer to windows where the glazed panels are opened by sliding vertically, or horizontally in a style known as a "Yorkshire light", sliding sash, or sash and case (so called because the weights are concealed in a box case).