title: What is the "realm" in basic authentication
body: <p>I'm setting up basic authentication on a php site and found <a href="http://php.net/manual/en/features.http-auth.php">this</a> page on the php manual showing the set up.  What does "realm" mean here in the header? </p>
  
  <pre><code>header('WWW-Authenticate: Basic realm="My Realm"');
  </code></pre>
  
  <p>Is it the page page being requested?</p>