A breadcrumb trail is a row of links near the top of a page. It might show the route from the homepage through a category to an article. In 2017 I wrote that this helps visitors who do not arrive through the homepage. That is common: someone follows a search result or a direct link to a deeper page.
Make the structure visible
Imagine a shop page for one particular camera. “Home › Cameras › Mirrorless cameras” provides immediate context. Someone seeking a different model can return to the category without deciphering the main menu. On a blog, the path might run through a topic and subtopic. It should reflect a real, useful route rather than an artificially long hierarchy.
Use understandable names for the steps. Each item pointing to a parent page should work as a link. The current page need not link to itself. On mobile, check that the path remains readable without pushing the main content too far down.
What about search engines?
Internal navigation links can help search engines understand site structure. Google also documents breadcrumb structured data that may make a page eligible for breadcrumb display in search results. It does not guarantee a particular appearance or a higher rank. Google no longer shows breadcrumbs in mobile search results, although they can still appear on desktop.
The best reason to add breadcrumbs is the visitor. If your site has several levels, they provide orientation and an easy way back. On a small site with few pages, they may add little. Judge them by actual navigation needs, not by hope for an SEO trick.