Bootstrap versions:
There are 4 release of bootstrap version from v1 through v4. See the following chart :

About Bootstrap 4:
- Bootstrap 4 is the latest and newest version of bootstrap.
- Bootstrap 4 used a flexbox to handle the layout. In the previous version means Bootstrap 3 used floats to handle the layout. For more details see bootstrap 3 vs bootstrap 4.
- Bootstrap 4 has some new components, faster stylesheet, effects, and more responsiveness.
- Bootstrap 4 supports some popular browser and platforms.
How to include or use Bootstrap 4 files on the web page:
There are 2 ways to include Bootstrap files in the website or web application as shown in the following :
- Include bootstrap 4 files From CDN link
- Download bootstrap 4 files library from https://getbootstrap.com and you can use it on the webpage.
Bootstrap 4 from CDN Link:
If you don’t want to download and host Bootstrap 4 files yourself, you can add it from a CDN (Content Delivery Network) Link.
MaxCDN provides CDN support for Bootstrap's overall CSS and JavaScript files and you must also add jQuery as shown in the following:
<!-- Latest compiled and minified CSS -->
<link rel=”stylesheet” href=”https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css”>
<!-- Latest compiled and minified jQuery library -->
<script src=”https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js”></script>
<!-- compiled and minified popper JS -->
<script src=”https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js”></script>
<!-- Latest compiled and minified JavaScript -->
<script src=”https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js”></script>
Why use jQuery and popper.js files?
Bootstrap 4 uses jQuery and Popper.js for JavaScript components such as navbar, modals, tooltips, popovers, Carousel, togging state, etc.
If you want to use or need only the CSS part of bootstrap then don’t include them on the webpage.
Download Bootstrap 4:
If you want to download and host Bootstrap 4 files yourself, then go to https://getbootstrap.com and follow the instructions there.
Creating Your First Webpage with Bootstrap 4:
Now we’re going to create a simple Bootstrap template by including the Bootstrap 4 CSS and JS files, as well as other JavaScript dependencies like jQuery and Popper.js via CDN.
In this example, you’ll have made a simple bootstrap 4 webpage that displays “My First webpage” message and 4 columns that have the same size in your web browser.
<!DOCTYPE html>
<html lang=”en”>
<head>
<title> 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/4.3.1/css/bootstrap.min.css”>
<script src=”https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js”></script>
<script src=”https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js”></script>
<script src=”https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js”></script>
</head>
<body>
<div class=”container”>
<div class=”row mx-auto”>
<h2 class=”mb-2″> My First webpage </h2>
</div>
<div class=”row”>
<div class=”col-sm-3″>
<h3> Column 1 </h3>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip…..</p>
</div>
<div class=”col-sm-3″>
<h3> Column 2 </h3>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip…..</p>
</div>
<div class=”col-sm-3″>
<h3> Column 3 </h3>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip…..</p>
</div>
<div class=”col-sm-3″>
<h3> Column 4 </h3>
<p> Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip…..</p>
</div>
</div>
</div>
</body>
</html>