Display
The display classes available help controll the visibility of content at various browser widths. If you wanted to only show a piece of content on tablets as an example, you could do that by using display classes.
Display Example (resize browser to demo):
This message will only show on small devices.
This message will show on medium devices.
This message will only show on large devices.
Code Example:
<div class="display-md-down">
<p class="alert alert-success">This message will only show on small devices.</p>
</div>
<div class="display-md-to-lg">
<p class="alert alert-danger">This message will show on medium devices.</p>
</div>
<div class="display-lg-up">
<p class="alert alert-warning">This message will only show on large devices.</p>
</div>