Definition
BreadcrumbList schema is a schema.org type that describes the trail of pages leading to the current one, home, then section, then page. Search engines use it to show a breadcrumb path in results instead of a bare URL.
Why it matters
Breadcrumbs make a result clearer and the site's structure legible to crawlers, which helps both rich results and how link equity flows through the site.
How we think about it
Every non-home page we build renders a breadcrumb with BreadcrumbList schema, generated from one builder, so the trail in search matches the trail on the page.