When editing Emacs Lisp code, you can use the commands C-h f
describe-function) and C-h v (
to view the built-in documentation for the Lisp functions and
variables that you want to use. See Name Help.
Eldoc is a buffer-local minor mode that helps with looking up Lisp documention. When it is enabled, the echo area displays some useful information whenever there is a Lisp function or variable at point; for a function, it shows the argument list, and for a variable it shows the first line of the variable's documentation string. To toggle Eldoc mode, type M-x eldoc-mode. Eldoc mode can be used with the Emacs Lisp and Lisp Interaction major modes.