An application frame , or simply a frame , is the locus of all application-specific knowledge. It is a physical, bordered object that is composed of smaller, individually functioning parts, called panes . The frame maintains information regarding the layout of these components, keeps track of the Lisp state variables that contain the state of the application, and optionally has an interface to the window manager.
In developing a simple application such as an on-line address book, the application frame could be divided into several units to accomplish various tasks, as you can see in 1.4.1.2. One pane could be used to accept commands; another section of the screen could provide an index of names in the address book; another portion could be used to display a specific address entry. We might also choose to have a general menu and a few conveniently placed scroll bars. Each of these components of the application frame is a pane
Common Lisp Interface Manager 2.0 User's Guide - 7 Aug 2017