Move to the right a little more, and you will see this expression:
You just learned that
ReactDOM.render makes its first argument appear onscreen. But where on the screen should that first argument appear?
The first argument is appended to whatever element is selected by the second argument.
In the code editor, select index.html. See if you can find an element that would be selected by
That element acted as a container for
ReactDOM.render's first argument! At the end of the previous exercise, this appeared on the screen: