For information about accordions please refer to Bootstrap's documentation.
Accordings are a group of .card elements:
html
<div class="accordion" id="myAccordion">
<div class="card">
<div class="card-header" id="headingOne">
<h2 class="card-title">
<a class="accordion-toggle" href="#collapseOne" data-toggle="collapse" aria-expanded="true" aria-controls="collapseOne">
<i class="fa fa-angle-right toggle-icon mr-1"></i>
Item #1
</a>
</h2>
</div>
<div id="collapseOne" class="collapse show" aria-labelledby="headingOne" data-parent="#myAccordion">
<div class="card-body">
Content # 1
</div>
</div>
</div>
.
.
.
</div>
You can also have custom styled accordions by using:
.btn-*classes on thea.accordion-toggleelement.bgc-*.brc-*.text-*classes on thea.accordion-toggleelement.bgc-*.brc-*.text-*classes on the.card-titleelement. Those colors will be applied toa.accordion-togglewhen it becomes 'expanded' (open)

html
<div class="card-header" id="headingOne">
<h2 class="card-title bgc-primary-l3 text-dark-tp3 brc-primary-tp1">
<a class="accordion-toggle btn btn-lighter-secondary brc-h-primary-m1 border-l-6 py-3 radius-0" href="#collapseOne6" data-toggle="collapse" aria-expanded="true" aria-controls="collapseOne6">
<i class="fa fa-angle-right toggle-icon mr-2 text-95"></i>
Item #1
</a>
</h2>
</div>
You can use custom icons by using Dynamic Styling:
html
<a class="d-style collapsed accordion-toggle" href="#collapseOne" data-toggle="collapse" aria-expanded="false" aria-controls="collapseOne2">
<span class="position-r mr-3">
<i class="far fa-plus-square d-collapsed"></i>
<i class="far fa-minus-square d-n-collapsed"></i>
</span>
Item #1
</a>
For rotating directional icons, you should add .toggle-icon and they can be any direction:
html
<a class="accordion-toggle" href="#collapseOne" data-toggle="collapse" aria-expanded="true" aria-controls="collapseOne">
<i class="fa fa-angle-down toggle-icon mr-1"></i>
Item #1
</a>