The term sash windows can be confusing. When learning about the structure of windows, it can help to use the comparison of a door’s structure. Both have casements that give stability and frame the entire structure. A door has a panel that opens and closes. Windows open and close differently, but the glass could be compared to the door panel, but it is fragile and needs something to safely contain it. The sash of a window is what frames the glass pane. Sash also can refer to the panel of glass and sash together as a unit. How the window opens and closes is what determines its style.
The basic styles of hinged window are casement, hopper, and awning styles. Casements crank outward on their hinged sides and are often called crank-outs. Hoppers are usually used in basements and are hinged on the bottom and open toward the inside. Awnings are hinged at the top and open toward the outside.
Another style of window more common in tropical climates is the louvered window. Many small lengths of glass panes are mounted in an overlapping horizontal pattern and are swiveled open for air circulation.