I'm a little new to emacs.
When looking at some of the configurations, I found there are two types command in "add-hook".

    (add-hook 'LaTeX-mode-hook #'LaTeX-math-mode)

and

    (add-hook 'LaTeX-mode-hook 'LaTeX-math-mode)

This has confused me for a long time and I don't know how to search "#'" in google...

Thanks.