<button>Open popup</button>

<div id="popup">
  <h2>I'm a popup</h2>
  <p>Lorem ipsum dolor sit amet consectetur adipisicing.</p>
</div>
Preview

Hints

<button popovertarget="popup">Open popup</button>

<div id="popup" popover>
  <h2>I'm a popup</h2>
  <p>Lorem ipsum dolor sit amet consectetur adipisicing.</p>
</div>