An ad network is a platform that connects advertisers with publishers who want to display ads on their websites or apps. It acts as an intermediary, helping advertisers reach their target audience while providing publishers with a way to monetize their content. By aggregating ad inventory from various publishers, ad networks can offer advertisers a broader reach. These networks use technology to match ads with relevant content, ensuring that the ads are shown to users who are likely to be interested. This process helps improve the effectiveness of advertising campaigns and maximizes revenue for publishers, creating a win-win situation for both parties involved.