GNU Emacs Lisp Reference Manual

20.1.4: Getting Help about a Major Mode

The describe-mode function is used to provide information about major modes. It is normally called with C-h m. The describe-mode function uses the value of major-mode, which is why every major mode function needs to set the major-mode variable.

Command: describe-mode

This function displays the documentation of the current major mode.

The describe-mode function calls the documentation function using the value of major-mode as an argument. Thus, it displays the documentation string of the major mode function. (See Accessing Documentation.)

Variable: major-mode

This variable holds the symbol for the current buffer's major mode. This symbol should have a function definition that is the command to switch to that major mode. The describe-mode function uses the documentation string of the function as the documentation of the major mode.