Is your head spinning from the last video?! If you didn't 100% get the previous video and you are still unsure what a runtime really is, how asynchronous code works, and what the event loop in Tokio is doing, we have provided an appendix section for you to show how browsers work and how things like setTimeout() aren't really part of JavaScript.

Simply go to the Bonus: How JavaScript Works section, watch the videos there, and once you are done, come back here and continue with the course. This is our recommended path to take!

PS if you already know these things, you can skip the Bonus: How JavaScript Works section and continue on with the next lecture :)