Is breadcrumbs are really needed in SEO? If yes can you pls explain how is useful to SEO.

Yes, breadcrumbs help users understand your website's navigation structure, which aids in the user experience. Search engines like sites that have a good user experience. Additionally, breadcrumbs help search engines themselves understand your website's navigation structure, and they feature this in the search result listings, which can increase clicks to your site from the SERPs.

A breadcrumb is a small text path, often located at the top of a page which is clickable for the way back to your wanted page. Breadcrumbs shows you which page your are. In short it is the structured data of your website.