what does a bootstrap loader do code example

Example 1: bootstrap loader

<div class="spinner-border text-primary" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-secondary" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-success" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-danger" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-warning" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-info" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-light" role="status">
  <span class="sr-only">Loading...</span>
</div>
<div class="spinner-border text-dark" role="status">
  <span class="sr-only">Loading...</span>
</div>

Example 2: bootstrap loader

<div class="spinner-grow" role="status">
  <span class="sr-only">Loading...</span>
</div>

Example 3: bootstrap loader

<div class="clearfix">
  <div class="spinner-border float-right" role="status">
    <span class="sr-only">Loading...</span>
  </div>
</div>