When creating a web application, or a web site with more than one page, you will need to reference different resources. If you create a blog, you need to create unique paths to all the blog posts, like we are doing in this Christmas calendar. You see that the url is https://security.christmas/2018/20, where 2018 is a reference to the year, and 20 to the day of December. It is a fairly simple system, and you may have tried to skip ahead, but been met by a page saying you have to wait a bit longer?
D3 (Data Driven Documents) is a JavaScript library that's well suited to create data visualizations on the web. It brings data to life using HTML, SVGs and CSS. You can make everything from static graphs to interactive articles.
A hot topic these days, and I don't think we'll ever agree, but here are some ways to do CSS in your React app