Here is a simple Mathematica notebook.

Here is the expression that corresponds to this notebook.

Notebook[{
 Cell["Section heading", "Section"],
 Cell["Some text.", "Text"],
 Cell["More text.", "Text"]}]

Just like individual cells, notebooks in Mathematica can also have options. You can look at and modify these options using the Option Inspector in the standard notebook front end.

A notebook with the option setting Saveable ->False can always be saved using the Save As menu item, but does not respond to Save and does not prompt for saving when it is closed.

In addition to notebook options, you can also set any cell option at the notebook level. Doing this tells Mathematica to use that option setting as the default for all the cells in the notebook. You can override the default by explicitly setting the options within a particular cell or by using a named style which explicitly overrides the option.

Here is the expression corresponding to a notebook with a ruler displayed in the toolbar at the top of the window.

Notebook[{
 Cell["Section heading", "Section"],
 Cell["Some text.", "Text"]},
 WindowToolbars->{"RulerBar"}]

This is what the notebook looks like in the front end.

This sets the default background color for all cells in the notebook.

Notebook[{
 Cell["Section heading", "Section"],
 Cell["Some text.", "Text"]},
 Background->GrayLevel[.7]]

Now each cell has a gray background.

If you go outside of Mathematica and look at the raw text of the file that corresponds to a Mathematica notebook, you will find that what is in the file is just the textual form of the expression that represents the notebook. One way to create a Mathematica notebook is therefore to construct an appropriate expression and put it in a file.

In notebook files that are written out by Mathematica, some additional information is typically included to make it faster for Mathematica to read the file in again. The information is enclosed in Mathematica comments indicated by (*...*) so that it does not affect the actual expression stored in the file.

This writes a notebook expression out to the file .

This reads the notebook expression back from the file.

This opens as a notebook in the front end.

Once you have set up a notebook in the front end using NotebookOpen , you can then manipulate the notebook interactively just as you would any other notebook. But in order to use NotebookOpen , you have to explicitly have a notebook expression in a file. With NotebookPut , however, you can take a notebook expression that you have created in the kernel, and immediately display it as a notebook in the front end.

Here is a notebook expression in the kernel.

This uses the expression to set up a notebook in the front end.

You can use NotebookGet to get the notebook corresponding to a particular NotebookObject back into the kernel.