A marks up a page's navigation path, that is, the sequence from the home page through categories down to the current page. It makes a URL's position within the site structure machine-readable.
This markup is typical on:
- blog posts,
- category and sub-pages,
- product pages.
In search it can produce a display in the result and makes the navigation structure clearer. If breadcrumbs are visible but not marked up as a BreadcrumbList, this structured information is missing.
The marked-up breadcrumb should match the visible path. Its priority is usually medium: BreadcrumbList complements core types such as Article, Product or Organization rather than replacing them.