A breadcrumb trail is a row of links, usually sitting just below the header, that shows where a page sits inside a site's structure: Home > Category > Subcategory > Page, each level clickable. It gives visitors a direct way to jump back up to a broader section instead of hunting through navigation menus, and it gives search engines the same hierarchy signal, reinforcing how pages relate to each other.
Sites with deep or complex category trees benefit the most, since breadcrumbs are often the only visible cue that a page sits three or four levels into the structure. Marking them up with BreadcrumbList structured data lets Google render the trail directly in the search result itself, replacing part of the raw URL with a clean path of clickable labels that can make a listing easier to scan. Because breadcrumbs give a lost or confused visitor an easy way back to familiar ground rather than the exit button, they're one of the simpler additions that can measurably help bounce rate on deeper pages.
