flyspell-mode

flyspell-mode is an interactive autoloaded compiled Lisp function in `flyspell.el'.

It is bound to <menu-bar> <tools> <spell> <flyspell-mode>.

(flyspell-mode &optional ARG)

Toggle on-the-fly spell checking (Flyspell mode).
With a prefix argument ARG, enable Flyspell mode if ARG is
positive, and disable it otherwise. If called from Lisp, enable
the mode if ARG is omitted or nil.

Flyspell mode is a buffer-local minor mode. When enabled, it
spawns a single Ispell process and checks each word. The default
flyspell behavior is to highlight incorrect words.

Bindings:
M-$: correct words (using Ispell).
M-x flyspell-auto-correct-word: automatically correct word.
M-x flyspell-auto-correct-previous-word: automatically correct the last misspelled word.
M-x flyspell-correct-word (or down-mouse-2): popup correct words.

Hooks:
This runs `flyspell-mode-hook' after flyspell mode is entered or exit.

Remark:
`flyspell-mode' uses `ispell-mode'. Thus all Ispell options are
valid. For instance, a different dictionary can be used by
invoking `ispell-change-dictionary'.

Consider using the `ispell-parser' to check your text. For instance
consider adding:
(add-hook 'tex-mode-hook (function (lambda () (setq ispell-parser 'tex))))
in your init file.

M-x flyspell-region checks all words inside a region.
M-x flyspell-buffer checks the whole buffer.