Auto-tagging is a method of tracking clicks on links to your website from external sources, such as search engines or other websites. It involves adding a tracking parameter to the URLs of your website, which is automatically appended to the URLs of any outbound links that point to your site. This tracking parameter allows you to track the source of the traffic, and it can be used to attribute conversions to the correct marketing channels and campaigns.
Auto-tagging is often used in conjunction with web analytics platforms, such as Google Analytics. These platforms can automatically read the tracking parameter and use it to attribute traffic and conversions to the correct channels and campaigns.