Google Publisher Tag (GPT) is a JavaScript library provided by Google that enables publishers to serve ads from Google Ad Manager (formerly DoubleClick for Publishers or DFP). It allows websites to dynamically request and display ads in a highly customizable manner. When a page loads, GPT requests ads from Google Ad Manager based on defined ad slots and targeting criteria. It supports various ad formats, including display, native, and video ads, and integrates with programmatic advertising platforms for real-time bidding. GPT asynchronously loads ads, which helps prevent display ads from slowing down page rendering. It also provides features for controlling ad refresh rates, targeting, and integrating with consent management platforms (CMPs) to ensure compliance with privacy regulations. This script primarily focuses on efficient ad delivery, managing ad inventory, and optimizing ad revenue for publishers by offering fine-grained control over ad requests and display. It interacts with Google's ad servers to fetch relevant ad creatives and track ad impressions and clicks.