What are breadcrumbs?
A breadcrumb is a trail on a page that indicates the page's position in the site hierarchy. Breadcrumbs make it useful for a user to navigate the site hierarchy, one level at a time, by starting from the last breadcrumb in the breadcrumb trail.
Breadcrumbs used with Schema markup with also add benefit to your search engine rankings, as well as better structure how your site appears in Google search results.
What Breadcrumbs look like
Home > About > Our team
In this example, the 'Our team' page is the page being viewed, and it would sit underneath the about us page in the navigation/site hierarchy.
How to activate Breadcrumbs
To activate Breadcrumbs on your site, go to: Administration > Settings > SEO > and scroll down till you see 'Show breadcrumbs'. Tick the show checkbox.
This will automatically insert breadcrumbs to the site.
More information from Google can be found here on the benefits of how Google see Breadcrumbs.