The Window menu lists all of the currently open windows in the application. Selecting a window from the Window menu makes it the active window. This option is useful when you have multiple windows open and you want to quickly bring one of the windows to the front.
Window | Close will close the actively selected window.
Window | Close All will close all open windows.
Window | Arrange All will arrange all windows with the Library Explorer visible from top to bottom on the left side and all other windows cascaded on the right.