The Breaker block is used to insert a new (bootstrap) row in a content area where you don't want the content further down the page to run on from any content used earlier in the page. You can't see these blocks - they don't output anything visible to the content area.
It might sound odd, but there are some reasons for this - I tend to use Breaker Blocks set-up with CSS classes so it's only visible in mobile views where we want to have a row of 3 on large displays, and rows of two on narrow displays.
If you don't do this, you tend to end-up with a row of two, and a row of one if the content of the sections isn't all the same height. You can achieve this in otherways, but using the breaker block is the quickest and doesn;t affect any of the other blocks in the content area (which may be used elsewhere on the site).