Cute Young Red Haired Girl Outside At The Window

A French window, also known as a French door is really a type of door, but one which has one or more panes of glass set into the whole length of the door, meaning it also functions as a window. In Italy they are very common, usually overlooking a terrace, known as portafinestra (door-window).
Technical terms
In insulated glass production, used to enter a house and/or building. The term "lite", or "light", refers to a glass pane, several of which may be used to construct the final window product. For example, a sash unit, consisting of at least one sliding glass component, is typically composed of two lites, while a fixed window is composed of one lite. The terms "single-light", "double-light" etc. refer to the number of these glass panes in a window.