title: What does the dollar sign ('$') mean when in the string to .query?
body: <p>What does the <code>$</code> sign mean in this statement:</p>
  
  <pre><code>// SQL Query &gt; Update Data
  client.query('UPDATE items SET text=($1), complete=($2) WHERE id=($3)',
  [data.text, data.complete, id]);
  </code></pre>