Google Tag Manager
Also known as: GTM
In short
A tag management system for configuring and deploying measurement and other supported tags through containers, triggers and variables.
Control when a tag runs
Google Tag Manager organizes tags and the conditions that activate them. A tag sends information or performs a supported action. A trigger determines when it runs. Variables supply values used by tags and trigger conditions.
A container holds that configuration. After the container is installed, many changes can be managed without editing individual page templates. The site still needs reliable events and data; a tag manager cannot infer every business outcome from a click.
A data layer can make those outcomes explicit by exposing structured information for the container to use.
Illustrative workflow
Imagine a fictional shop publishing a confirmed-purchase event with an order value and currency. A trigger responds to that event, and variables pass the relevant values to a measurement tag.
The team previews the configuration, checks the values and verifies receipt in the destination system before treating the change as complete.
Avoid measuring the wrong success
A button click can start an action that later fails. Use a confirmed outcome when the metric is meant to represent completion. Check for duplicate tags, missing values and the required consent behavior. Seeing a tag fire in a debugging interface proves that code ran; it does not by itself prove that the receiving report contains the correct business event.