Windows and Frames

For those of you not familiar with Emacs lingo, an Emacs frame is what most window managers would call a window, while an Emacs window is any of the regions displaying a buffer inside a frame. Usual ways of creating windows in Emacs are C-x 2, C-x 3, C-x 4 f, and so on. See EmacsWiki:Window and EmacsWiki:WindowsAndFrames for more.

—http://emacs.wordpress.com/2007/01/28/simple-window-configuration-management/