If you work with Javascript, either in the browser, or via Node.js then Philip Robers talk "What the heck is the event loop anyway?" it worth 26 mins of your day.
JavaScript programmers like to use words like, “event-loop”, “non-blocking”, “callback”, “asynchronous”, “single-threaded” and “concurrency”.
...
If you’re anything like me, you nod and agree, as if it’s all obvious, even though you don’t actually know what the words mean; and yet, finding good explanations of how JavaScript actually works isn’t all that easy, so let’s learn!