In practice
Mirror the real category structure, not the path the visitor happened to take, and mark it up with BreadcrumbList.
Marked-up breadcrumbs replace the raw URL in search results, which reads far better on long paths.
Why it matters
They pass internal links upward to category pages on every single product or article page.
They give a visitor arriving from search an immediate sense of context, which reduces the bounce straight back to results.