provides optional features that users may enable or disable independently of the choice of major mode. Minor modes can be enabled individually or in combination with other modes.
A minor-mode is one of two main modes in Emacs for grouping definitions and customizing editing features. Modes can be turned on and off while editing. They are not just a programming feature, but an essential part of Emacs interaction.
A minor-mode can be enabled individually or in combination with other modes. Most minor modes handle features independent of the major-mode. Some modes depend on each other, but those are exceptions.
A minor-mode can have its own keymap and visual cues in the modeline.
A typical Emacs installation could have a dozen or more minor modes. C-h v minor-mode-list
shows a complete list.