title: in this code below tr("%1") and .arg() does here?
body: <p>I know <code>tr()</code> is used for language translation but what does <code>"%1"</code> do here?
   What's the purpose of <code>.arg()</code> in the code below?</p>
  
  <pre><code> tmpItem= new QTableWidgetItem(tr("%1").arg(query.value(0).toString()));
  </code></pre>