http://www.gnu.org/software/emacs/elisp/html_node/Scope.html http://www.gnu.org/software/emacs/elisp/html_node/Scope.html http://www.gnu.org/software/emacs/ema

http://www.gnu.org/software/emacs/elisp/html_node/Scope.html http://www.gnu.org/software/emacs/elisp/html_node/Scope.html http://www.gnu.org/software/emacs/emacs-paper.html#SEC17 http://www.gnu.org/software/emacs/emacs-paper.html#SEC17 The docs and the man himself say it best.