I've noticed that when I inspect code made with bootstrap classes, there tends to be lots of ::after and ::before properties in the CSS. An example is below (from w3schools site).
Could someone please explain in broad terms what these extra properties are designed to achieve, and why they seem to appear on almost all elements?
From what I can tell, they are making all excluded elements into table elements and adding an empty space of text. I assume this if for layout purposes, but I'd love to learn more about the reasons it's done.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h1>Grid</h1>
<p>This example demonstrates a 50%/50% split on small, medium and large devices. On extra small devices, it will stack (100% width).</p>
<p>Resize the browser window to see the effect.</p>
<div class="row">
<div class="col-sm-6" style="background-color:yellow;">
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.<br>
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
</div>
<div class="col-sm-6" style="background-color:pink;">
Sed ut perspiciatis unde omnis iste natus error sit voluptatem accusantium doloremque laudantium, totam rem aperiam, eaque ipsa quae ab illo inventore veritatis et quasi architecto.
</div>
</div>
</div>
</body>
</html>
