The Google Chrome Development tools are very useful if you want to understand and learn about web programming.
The tools are integrated in the Chrome web browser and you can find them easily selecting the View Menu, then Developer and Developer Tools.
console.log(....) will print anything you ask it to print in between the parentheses. But methods and functions also have return values (like an output). If the function has nothing to return, it will often write "
undefined", no worries if you read this message.