CSS

what does clearfix for floats do in css

/* A clearfix is a way for an element 
to clear its child elements automatically without any additional markup.
The clearfix property is generally used in float layouts where elements 
are floated to be stacked horizontally. ... The clearfix property allows
a container to wrap its floated children.
*/

.clearfix {
  overflow: auto;
}

css clearfix for floats with display table and clear both

.group:after {
  content: "";
  display: table;
  clear: both;
}

<div class="group">
  <div class="is-floated"></div>
  <div class="is-floated"></div>
  <div class="is-floated"></div>
</div>