How to get the mode-specific help information or help files

Question

No matter in which mode I am currently in, is there a general way / key combination to open the help file related to the currently active mode?

Answer 1

There's M-x describe-mode, which is bound to C-h m by default. It shows the current major mode, as well as all current minor modes.

If you want to jump directly to the description of your current major mode, then either evaluate (describe-function major-mode) (via M-:) or bind it to a key, for example:

(defun my/describe-current-major-mode ()
  "Describe the current major mode via `describe-function'"
  (interactive)
  (describe-function major-mode))

(global-set-key (kbd "<f5>") #'my/describe-current-major-mode)