BreadcrumbList (schema.org)
BreadcrumbList is a schema.org type that marks up the hierarchical navigation path of a page (for example Home > Category > Subpage) in a machine-readable way for search engines.
In practice
Correctly marked-up breadcrumbs can appear in search results in place of the bare URL and show readers and search engines alike where a page sits within the website structure – particularly helpful on deeply nested category and glossary pages.