Emacs/emacs/Easy-Customization

From Get docs

49.1 Easy Customization Interface

Emacs has many settings which you can change. Most settings are customizable variables (see Variables), which are also called user options. There is a huge number of customizable variables, controlling numerous aspects of Emacs behavior; the variables documented in this manual are listed in Variable Index. A separate class of settings are the faces, which determine the fonts, colors, and other attributes of text (see Faces).

To browse and alter settings (both variables and faces), type M-x customize. This creates a customization buffer, which lets you navigate through a logically organized list of settings, edit and set their values, and save them permanently.

Customization Groups:    How settings are classified.
Browsing Custom:    Browsing and searching for settings.
Changing a Variable:    How to edit an option’s value and set the option.
Saving Customizations:    Saving customizations for future Emacs sessions.
Face Customization:    How to edit the attributes of a face.
Specific Customization:    Customizing specific settings or groups.
Custom Themes:    Collections of customization settings.
Creating Custom Themes:    How to create a new custom theme.