Callouts provide contextual messages to draw attention of the user. See the examples below:
I have a message for you, but not so important.
I have a message that may help you to understand better.
I have a warning for you. Be careful.
I have a critical message for you. This is really important.
<div class="callout">
<h5>Basic</h5>
<p>I have a message for you, but not so important.</p>
</div>
<div class="callout callout-info">
<h5>Good</h5>
<p>I have a message that may help you to understand better.</p>
</div>
<div class="callout callout-warning">
<h5>Warning</h5>
<p>I have a warning for you. Be careful.</p>
</div>
<div class="callout callout-danger">
<h5>Critital</h5>
<p>I have a critical message for you. This is really important.</p>
</div>