I am configuring AUCTeX in emacs.

Most of the configurations are put in a LaTeX-mode-hook. When I open a main.tex file, I notice that the major mode is latex-mode and my hooked configurations are not activated. I have to M-x Tex-latex-mode to activate them. But the major-mode is still latex-mode. 

```
(add-hook 'LaTeX-mode-hook
      (lambda ()

        ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
        ;; auctex

        (setq TeX-auto-save t)
        (setq TeX-parse-self t)
       ))

```

So I would like to know what is the difference of these modes and how can I turn on AUCTeX automatically when I open a \*.tex file.