title: What does serial.begin() do?
body: <p>I'm confused about the purpose of <code>serial.begin()</code>. For instance:</p>
  
  <pre><code>serial.begin(baud)
  </code></pre>
  
  <p>Where 'baud' refers to baud rate.</p>
  
  <p>What is the purpose of this function?</p>