Customization settings are organized into customization
groups. These groups are collected into bigger groups, all the way
up to a master group called Emacs.
M-x customize creates a customization buffer that shows the
top-level Emacs group. It looks like this, in part:
For help using this buffer, see [Easy Customization] in the [Emacs manual].
________________________________________ [ Search ]
Operate on all settings in this buffer:
[ Revert... ] [ Apply ] [ Apply and Save ]
Emacs group: Customization of the One True Editor.
[State]: visible group members are all at standard values.
See also [Manual].
[Editing] Basic text editing facilities.
[Convenience] Convenience features for faster editing.
...more second-level groups...
The main part of this buffer shows the ‘Emacs’ customization group, which contains several other groups (‘Editing’, ‘Convenience’, etc.). The contents of those groups are not listed here, only one line of documentation each.
The state of the group indicates whether setting in that group has been edited, set, or saved. See Changing a Variable.
Most of the customization buffer is read-only, but it includes some editable fields that you can edit. For example, at the top of the customization buffer is an editable field for searching for settings (see Browsing and Searching for Settings). There are also buttons and links, which you can activate by either clicking with the mouse, or moving point there and typing RET. For example, the group names like ‘[Editing]’ are links; activating one of these links brings up the customization buffer for that group.
In the customization buffer, you can type TAB
(widget-forward) to move forward to the next button or editable
field. S-TAB (widget-backward) moves back to the
previous button or editable field.