title: what does app.use(cors()) do?
body: <p>I know that we cannot have access to an API that has different domain there ours. However, I see many people installing the <code>cors</code> module in express to use APIs and then using it like so:</p>
  
  <pre><code>app.use(cors());
  </code></pre>
  
  <p>What does it actually do? How does this function enable <code>cors</code> on the server?</p>