what does clearfix for floats do in css

1/* A clearfix is a way for an element 
2to clear its child elements automatically without any additional markup.
3The clearfix property is generally used in float layouts where elements 
4are floated to be stacked horizontally. ... The clearfix property allows
5a container to wrap its floated children.
6*/
7
8.clearfix {
9  overflow: auto;
10}

1.group:after {
2  content: "";
3  display: table;
4  clear: both;
5}
6
7<div class="group">
8  <div class="is-floated"></div>
9  <div class="is-floated"></div>
10  <div class="is-floated"></div>
11</div>