Google Tag Manager, or GTM, is a free tool for adding and managing tracking code, analytics snippets, conversion pixels, custom scripts, without editing a site's actual codebase every time something needs to change. One container snippet goes into the site once; everything else gets configured and deployed through GTM's own interface.
That separation is the whole value proposition. A marketing team can add a new conversion tracker or adjust an existing tag without filing a developer ticket, and changes can be tested in a preview mode and rolled back instantly if something breaks, rather than needing a code deploy either way. GTM commonly sits in front of Google Analytics, Google Ads conversion tracking, and any number of third-party marketing or analytics tools, acting as the single place where all of a site's tracking logic lives and can be audited, rather than that logic being scattered across dozens of hardcoded snippets throughout the codebase.
