describe-mode

describe-mode is an interactive compiled Lisp function in `help.el'.

It is bound to C-h m, <f1> m, <help> m, <menu-bar> <help-menu> <describe> <describe-mode>.

(describe-mode &optional BUFFER)

Display documentation of current major mode and minor modes.
A brief summary of the minor modes comes first, followed by the
major mode description. This is followed by detailed
descriptions of the minor modes, each on a separate page.

For this to work correctly for a minor mode, the mode's indicator
variable (listed in `minor-mode-alist') must also be a function
whose documentation describes the minor mode.

If called from Lisp with a non-nil BUFFER argument, display
documentation for the major and minor modes of that buffer.