How to replace regexp in buffers in Emacs Lisp?

Note: Although it works, how I used replace-regexp in this video is not recommended in Elisp programs in general.

(replace-regexp "-b" "^^^^")
(replace-regexp "-b" "^^^^" nil (point-min) (point-max))
(replace-regexp "-b" "^^^^" nil (point-at-bol) (point-at-eol))