Breadcrumbs

What are they

Breadcrumbs are intended to show your visitors what page they're on and how they got there.  In the most simple form, it will show your visitor the current category they're on, along with filters that exist.  

Category

https://demo.auroracommerce.com/books/

Filter

https://demo.auroracommerce.com/books/p:0-10/

Product Details Page

https://demo.auroracommerce.com/toidvd5/toidvd5

The breadcrumbs will only appear on a product details page if you have come from a category page. If you land directly, it will not know what path you came from, so will not display.