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 typical Emacs installation could have a dozen or more minor modes.
C-h v minor-mode-list shows a complete list.