I have a quick walkthrough of notebooks:
Remember chemistry class in high school or college? You might remember having to keep a lab notebook for your experiments. The purpose of this notebook was two-fold: first, so you could remember what you did and why you did each step; second, so others could repeat what you did. A well-done lab notebook has all you need to replicate an experiment, and independent replication is a huge part of what makes hard sciences “hard.”
Take that concept and apply it to statistical analysis of data, and you get the type of notebook I’m talking about here. You start with a data set, perform cleansing activities, potentially prune elements (e.g., getting rid of rows with missing values), calculate descriptive statistics, and apply models to the data set.
I didn’t realize just how useful notebooks were until I started using them regularly.