Clarify the function of Jupyter Notebooks in the introduction

[MLDERES]

Is this a Jupyter Notebook or is this a book with code samples? When this was first written the intention was that it is a collection of notebooks meant to be run and interacted with, but in that way it was missing the structure and continuity of a book. Pulling it into a book gave the structure necessary for the book to be useful, but it means the language in many places and the expectations of the user change as well - like why would I tell the user to run a particular cell, if the goal is to show how a notebook works?

It might be best to address this up-front and give enough details to remind users that going to a platform where they can run the book will be best in some cases (and calling out these cases).

Suggestion: Be clear about the function of the notebook on this page and then make a call out to where a user really ought to run the book on Jupyter or Binder in order to have a better experience.