title: What is routing? Why is "routing" needed in single page web apps?
body: <p>I understood that routing libraries for SPAs like <a href="https://github.com/ReactTraining/react-router" rel="noreferrer">https://github.com/ReactTraining/react-router</a> help to parse the URL and put the app into a corresponding state of a state machine.</p>
  <p>Is there more to routing than this?</p>
  <p>Why is routing needed in the first place?</p>
  <p>Why are URLs important? For example in a desktop app there are no URLs, so what's the big deal about them in a web app?</p>