Explain tag sequencing in Google Tag Manager and provide a realistic example of when it would be critical to use.

Tag sequencing in Google Tag Manager (GTM) allows you to define the order in which tags are fired. You specify a 'setup tag' which must fire *beforea primary tag, and a 'cleanup tag' which fires *afterthe primary tag, regardless of whether the primary tag succeeds or fails. This ensures that dependencies between tags are properly managed and that tags fire in the correct order. The primary tag is the tag that you want to track a specific event or action. The setup tag is a tag that performs any necessary setup or configuration before the primary tag fires. The cleanup tag performs any necessary cleanup or post-processing after the primary tag fires. It's critically important to use it when you have a tag that relies on a script or a variable that is set by another tag. If the tag fires before the script is loaded or the variable is set, then it will fail, and the data will not be tracked. A realistic example of when tag sequencing is critical is when implementing a custom event tracking solution that relies on a JavaScript library loaded via a custom HTML tag. Suppose you want to track user interactions with a video player embedded on your website, and you are using a JavaScript library called 'VideoTracker.js' to handle the video tracking logic. First, you would create a custom HTML tag that loads the 'VideoTracker.js' library. Second, you would create a Google Analytics event tag that tracks video play events. This tag relies on the 'VideoTracker.js' library to be loaded and initialized before it can track the video play events. Without tag sequencing, the Google Analytics event tag might fire before the 'VideoTracker.js' library is loaded, resulting in missing or inaccurate data. To prevent this, you would configure tag sequencing as follows: The custom HTML tag that loads the 'VideoTracker.js' library would be the setup tag. The Google Analytics event tag would be the primary tag. You would configure the Google Analytics event tag to fire *afterthe custom HTML tag. This ensures that the 'VideoTracker.js' library is always loaded and initialized before the Google Analytics event tag attempts to track video play events. By using tag sequencing, you can ensure that the dependencies between tags are properly managed and that tags fire in the correct order, leading to accurate and reliable data collection.