title: Lack of explanation to Google Sign-In documentation
body: <p>I'm reading the docs about <a href="https://developers.google.com/identity/sign-in/web/" rel="nofollow noreferrer">google Oauth2 sign-in</a>. </p>
  
  <p>Here's the confusing part: </p>
  
  <pre><code>    var profile = googleUser.getBasicProfile();
      console.log("ID: " + profile.getId()); // Don't send this directly to your server!
      console.log('Full Name: ' + profile.getName());
  </code></pre>
  
  <p>What's stored in <code>profile.getId</code> and what happens if I send it? </p>
  
  <p>What is stored in <code>id_token</code> instead? I would like to have explanations instead of recommendations in comments.  </p>
  
  <pre><code>    // The ID token you need to pass to your backend:
      var id_token = googleUser.getAuthResponse().id_token;
  </code></pre>
  
  <p>Bonus question: does Google return the same <code>id_token</code> every time I log in using same account?  </p>