defgroup

defgroup is a Lisp macro in `custom.el'.

(defgroup SYMBOL MEMBERS DOC &rest ARGS)

Declare SYMBOL as a customization group containing MEMBERS.
SYMBOL does not need to be quoted.

Third argument DOC is the group documentation. This should be a short
description of the group, beginning with a capital and ending with
a period. Words other than the first should not be capitalized, if they
are not usually written so.

MEMBERS should be an alist of the form ((NAME WIDGET)...) where
NAME is a symbol and WIDGET is a widget for editing that symbol.
Useful widgets are `custom-variable' for editing variables,
`custom-face' for edit faces, and `custom-group' for editing groups.

The remaining arguments should have the form

[KEYWORD VALUE]...

For a list of valid keywords, see the common keywords listed in
`defcustom'.

See Info node `(elisp) Customization' in the Emacs Lisp manual
for more information.