The "notebook" he refers to is the web page itself. It's a format that's becoming popular among Python / data science folks: a web-based, often interactive layo

The "notebook" he refers to is the web page itself. It's a format that's becoming popular among Python / data science folks: a web-based, often interactive layout with code and results embedded in it. See "Jupyter Notebook", the viewer for which is what you're viewing as you read this.