** Emacs has a new facility for customization of its many user
options. It is called M-x customize. With this facility you can look
at the many user options in an organized way; they are grouped into a
tree structure.
M-x customize also knows what sorts of values are legitimate for each user option and ensures that you don't use invalid values.
With M-x customize, you can set options either for the present Emacs session or permanently. (Permanent settings are stored automatically in your .emacs file.)