Check out example codes for "how to create popup css". It will help you in understanding the concepts better.

Code Example 1

<div class="popup" onclick="myFunction()">Click me!
  <span class="popuptext" 
id="myPopup">Popup text...</span>
</div>

Code Example 2

/* Popup container */
.popup {
  position: relative;
  display: inline-block;
  cursor: pointer;
}

/* The actual popup (appears on top) 
*/
.popup .popuptext 
{
  visibility: hidden;
  width: 
160px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 8px 0;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;

    
margin-left: -80px;
}

/* Popup arrow */
.popup .popuptext::after {
  content: "";

    position: absolute;
  
top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;

    border-color: #555 transparent 
transparent transparent;
}

/* 
Toggle this class when clicking on the popup container (hide and show the 
popup) */
.popup .show {
  
visibility: visible;
  -webkit-animation: 
fadeIn 1s;
  animation: fadeIn 1s
}

/* Add animation (fade in the popup) */

@-webkit-keyframes fadeIn {
  from {opacity: 0;} 
  to {opacity: 1;}
}


@keyframes fadeIn {
  from {opacity: 0;}
  
to {opacity:1 ;}
}

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