Since we are using JavaScript in this book, why not explore a little bit more how the language works?
When we open a new tab in the browser, a task queue is created. This is because only a single thread handles all the tasks for a single tab, and it is called an event loop. The browser is responsible for several tasks, such as rendering the HTML, executing JavaScript code commands, handling user interaction (user input, mouse clicks, and so on), executing and processing asynchronous requests. You can learn more about the event loop at the following link: https://goo.gl/ayF840 .
It is really nice to know that a popular and powerful language such as JavaScript uses such a basic data structure to handle internal control.