This panel contains a div element, which is hidden by default (display: none).
It is styled with CSS and we use JavaScript to show it (display: block).
How it works: Notice that the p element with class="flip" has an onclick attribute attached to it. When the user clicks on the p element, a function called myFunction() is executed, which changes the style of the div with id="panel" from display:none (hidden) to display:block (visible).
You will learn more about JavaScript in our JavaScript Tutorial.