elisp: Window Type

 
 2.4.3 Window Type
 -----------------
 
 A “window” describes the portion of the terminal screen that Emacs uses
 to display a buffer.  Every window has one associated buffer, whose
 contents appear in the window.  By contrast, a given buffer may appear
 in one window, no window, or several windows.
 
    Though many windows may exist simultaneously, at any time one window
 is designated the “selected window”.  This is the window where the
 cursor is (usually) displayed when Emacs is ready for a command.  The
 selected window usually displays the current buffer (SeeCurrent
 Buffer), but this is not necessarily the case.
 
    Windows are grouped on the screen into frames; each window belongs to
 one and only one frame.  SeeFrame Type.
 
    Windows have no read syntax.  They print in hash notation, giving the
 window number and the name of the buffer being displayed.  The window
 numbers exist to identify windows uniquely, since the buffer displayed
 in any given window can change frequently.
 
      (selected-window)
           ⇒ #<window 1 on objects.texi>
 
    SeeWindows, for a description of the functions that work on
 windows.