What's the definition of a tag, as it pertains to digital advertising?

The selection is correct because a modern tag is defined as a small snippet of code that's placed on every page of a website to ensure consistent and comprehensive data collection throughout the entire user journey. While older measurement methods often relied on placing code only on specific "Thank You" or conversion pages, current best practices—such as using the Google tag (gtag.js)—require sitewide implementation to accurately track arrivals, maintain first-party cookie data, and capture attribution signals across multiple sessions. By residing on every page, the tag can effectively bridge the gap between an initial ad click and a final conversion, providing the necessary technical foundation for features like enhanced conversions and sitewide attribution while improving the overall reliability of the measurement data.