A hook allows you to wedge your own pieces of Lisp code into the
operation of other functions, enable the extension of that
functionality. These pieces of code are evaluated via the hook and the
result is available to the hook’s caller. One hook has already been
format-hooks-alist variable (see Formatted Output).
|• Functions As Hooks:||Some hooks are a single function,|
|• Normal Hooks:||Others may be a list of pieces of code to evaluate.|