The Google Display Network (GDN) is the #1 ad network, reaching 89% of internet users worldwide. It allows advertisers to place text, image, video, and mobile ads across Google's vast network. Advertisers can increase their reach through unique targeting options like keywords, placements, audiences, and topics. Key considerations for running successful GDN campaigns include: setting up separate campaigns for search and display; using negative keywords for contextual targeting; reviewing placement performance to exclude underperforming categories; and testing different ad formats and variations to prevent ad fatigue. Proper conversion tracking and analytics integration are also important for measurement and optimization.