Chrome でのデスクトップ通知はどのように機能しますか?

<code class="js">document.addEventListener('DOMContentLoaded', function() {
  if (!Notification) alert('Desktop notifications not available in your browser.');
  if (Notification.permission !== 'granted') Notification.requestPermission();
});

function notifyMe() {
  if (Notification.permission === 'granted') {
    var notification = new Notification('Notification title', {
      icon: 'icon.png',
      body: 'Hey there! You\'ve been notified!',
    });
    notification.onclick = function() {
      window.open('http://example.com');
    };
  } else Notification.requestPermission();
}</code>

<code class="html"><button onclick="notifyMe()">Notify me!</button></code>