What is Use of dropdown-toggle class in dropdown - twitter-bootstrap-3

Question

Please help me to understand the use of "dropdown-toggle" class in dropdown. In the code below, I have removed the "dropdown-toggle" class. Without this also dropdown is working fine. Then What is use of this class.
<div class="container-fluid">
<h1>Hello, world!</h1>
<div class="dropdown">
<button type="button" class="btn btn-info" data-toggle="dropdown">MENU</button>
<ul class="dropdown-menu">
<li>ITEM-1</li>
<li>ITEM-1</li>
<li>ITEM-1</li>
<li>ITEM-1</li>
</ul>
</div>

Answer 1

The dropdown-toggle class adds the outline: 0; on :focus to the button, so when you click on the button it will not have the surrounding blue border of the "active" element.
Look on the the sample example below:
<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/3.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<div class="container">
<h2>Dropdowns</h2>
<p>The .divider class is used to separate links inside the dropdown menu with a thin horizontal line:</p>
<div class="dropdown">
<button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">Tutorials - no border
<span class="caret"></span></button>
<ul class="dropdown-menu">
<li>HTML</li>
<li>CSS</li>
<li>JavaScript</li>
<li class="divider"></li>
<li>About Us</li>
</ul>
</div>
</div>
<div class="container">
<h2>Dropdowns</h2>
<p>The .divider class is used to separate links inside the dropdown menu with a thin horizontal line:</p>
<div class="dropdown">
<button class="btn btn-default" type="button" data-toggle="dropdown">Tutorials - with border
<span class="caret"></span></button>
<ul class="dropdown-menu">
<li>HTML</li>
<li>CSS</li>
<li>JavaScript</li>
<li class="divider"></li>
<li>About Us</li>
</ul>
</div>
</div>