explanation of bootstrap grid system code example

Example 1: bootstrap grid

<div class="container">
  <div class="row">
    <div class="col-sm">
      One of three columns
    </div>
    <div class="col-sm">
      One of three columns
    </div>
    <div class="col-sm">
      One of three columns
    </div>
  </div>
</div>

Example 2: bootstrap grid class

col-12 col-sm-4 col-md-3 col-lg-12	col-xl-12