Google Tag Manager

Google Tag Manager is a program which serves to automaticly
create and modify tracking-tags for a website,
so as to track the actions of individual users on a website,
on behaf of the website-owner.

However, that program is run off-site at Google's website googletagmanager.com,
which means that the Google company is the primary recipient of that user-activity data,
which Google stores in its vast database of profiles.
In turn, Google shares that information with its affiliated intelligence-agencies,
namely the U.S. NSA, the german KSA, and probably one or more other agencies.
Google Tag Manager may also contain code that can circumvent proxies and VPNs.

Google Tag Manager was created by Google, and made freely available
(so that it woud dominate the tag-manager market), in 2012, at the behest of the NSA,
three years after the NSA takeover of Google in 2009.

Probably the single biggest user of Google Tag Manager is the major wiki-farm website
fandom.com, which Google and the intelligence agencies strongly desire to watch.