title: What is the react-native webserver and why is it needed?
body: <p>If I type the following:</p>
  
  <pre><code>react-native start --help
  </code></pre>
  
  <p>this is what I get:</p>
  
  <pre><code>react-native start [options]
  starts the webserver
  </code></pre>
  
  <p>Eh, what webserver? Why do I need one? How is it being used when I type <code>react-native run-android</code>?</p>