title: Javascript event loop: Where do web api's get executed?
body: <p>In reading about the JS event loop, I was curious where web api's get executed. For example, in this <a href="http://blog.carbonfive.com/wp-content/uploads/2013/10/event-loop.png" rel="noreferrer">image</a>, the pink box doesn't have a name (just says "implementation specific"), leaving me to wonder <em>where</em> these web api's get executed.  The call stack, event loop, message queue all have names. I've also seen Philip Roberts <a href="https://www.youtube.com/watch?v=8aGhZQkoFbQ" rel="noreferrer">talk</a> about the event loop and he just refers to it as a "Web API".</p>
  
  <p>So when a web api is reached in the call stack, it goes off and gets executed while the rest of the call stack gets run. But where does that web api call go to be executed? For example, if there's a set time out of 5 seconds, where is it sitting for those 5 seconds?</p>