Wolfram Notebook Tutorial
The Notebook is the Graphical User Interface app, can display graphics, or rotate graphics, press buttons, sliders, math typesetting, organized presentation like html, play sound from functions, etc. One can think of it as IDE for Wolfram Language.


Wolfram Notebook File Format
The entire notebook, is just a plain ASCII text file, of Wolfram Language expression. It is pure Wolfram Language, one giant single nested Wolfram Language expression. No special formatting.
When one use the notebook to open a Wolfram Language code that represent notebook, the notebook frontend renders them in a particular way, very much like how browser renders html. So, Wolfram Language is like html or TeX, while the notebook is like browser. This is also similar to org mode code in emacs.
For example, if you use a text editor to open a notebook, you'll see this:
Notebook[{Cell[...], Cell[...], ...}]
The
Notebook
,
Cell
are both just Wolfram Language functions.
WolframLang is like html+css+js, and notebook is like browser. It is the WolframLang, that controls everything. like how discord is the electron engine which is just a google chrome browser, with JavaScript code controlling everything. Also, lisp to emacs, is like WolframLang to notebook.
