Now that you have some grasp of React elements, we can explain React components, which are JavaScript functions or ES6 classes that accept arbitrary inputs (props) and return the React elements ...

Another interesting new concept in ES6 called Modules is something that JavaScript developers have been using for years. Some projects, like Webpack, let you take advantage of modularization now.

No examples using ES6 syntax. All of the examples use ES5 syntax, which feels kludgy after working with better language ergonomics for years.