In this chapter, you learned what D3 is and took a glance at the core philosophy behind how it works. You also set up your computer for prototyping of ideas and to play with visualizations. This environment will be assumed throughout the book.
We went through a simple example and created an animated histogram using some of the basics of D3. You learned about scales and axes, that the vertical axis is inverted, that any property defined as a function is recalculated for every data point, that we use a combination of CSS and SVG to make things beautiful. We also did a lot of fancy stuff with ES2017, Babel, and Webpack, and got Node.js installed. Go us!
Most of all, this chapter has given you the basic tools so that you can start playing with D3.js on your own. Tinkering is your friend! Don't be afraid to break stuff--you can always reset to a chapter's default state by running $ git reset --soft origin/chapter1, replacing 1 with whichever chapter you're on.
Next, we'll be looking at all this in a bit more in depth, specifically how the DOM, SVG, and CSS interact with each other. This chapter discussed quite a lot, so if some parts got away from you, don't worry. Just power through to the next chapter, and everything will start to make a lot more sense.