The HTTP Referer request header contains the absolute or partial address from which a resource has been requested. The Referer header allows a server to identify referring pages that people are visiting from or where requested resources are being used. This data can be used for analytics, logging, optimized caching, and more.| MDN Web Docs
The HTML element (or anchor element), with its href attribute, creates a hyperlink to web pages, files, email addresses, locations in the same page, or anything else a URL can address.| MDN Web Docs
The HTML element specifies relationships between the current document and an external resource. This element is most commonly used to link to stylesheets, but is also used to establish site icons (both "favicon" style icons and icons for the home screen and apps on mobile devices) among other things.| MDN Web Docs
3. Referrer Policies| w3c.github.io