What's the difference between event.stopPropagation and event.preventDefault?

1 <div class='parent' onclick='alert(`parent`)'>
2   <div class='child' onclick='clickChild(event)'>child</div>
3 </div>
4  <script>
5    function clickChild(e) {
6      alert('child');
7      e.stopPropagation();
8    }
9  </script>