As you edit Lisp code to be run in Emacs, you can use the commands
C-h f (
describe-function) and C-h v
describe-variable) to print documentation of functions and
variables you want to call. These commands use the minibuffer to
read the name of a function or variable to document, and display the
documentation in a window.
For extra convenience, these commands provide default arguments based on the code in the neighborhood of point. C-h f sets the default to the function called in the innermost list containing point. C-h v uses the symbol name around or adjacent to point as its default.
The M-x manual-entry command gives you access to documentation
on Unix commands, system calls, and libraries. The command reads a
topic as an argument, and displays the Unix manual page for that topic.
manual-entry always searches all 8 sections of the
manual and concatenates all the entries it finds. For example,
the topic ‘termcap’ finds the description of the termcap library
from section 3, followed by the description of the termcap data base
from section 5.