A breadcrumb is a small trail of links that shows where someone is inside a website. Like a trail of signs in a building, it helps people understand how they got to the current room and how to go back up a level.
For example, a shop page might show Home, then Shoes, then Hiking Shoes. The current page is usually named last, while the earlier names link to broader sections.
Use breadcrumbs when pages have clear levels. They do not replace the main navigation or the browser's Back button; they are an extra map for the site's own structure.