title: What does 'the URL is local' mean?
body: <p>I am debugging some code and there is this check (in an ASP.NET MVC controller)</p>
  
  <pre><code>if (Url.IsLocalUrl(returnUrl))
  </code></pre>
  
  <p>So I check the documentation and it says
  <em>Returns a value that indicates whether the URL is local.</em></p>
  
  <p><strong>But what does that mean, 'the URL is local'?</strong></p>
  
  <p>If I hit a webserver, when does the webserver say 'the URL is local' ?</p>