A third-party company that connects websites that want to monetize their ad inventory with the appropriate advertisers. Ad networks aggregate publishers into content categories (travel, home and garden, sports) and then find the corresponding advertisers who want to buy that ad inventory at a high volume for a lower price, enabling advertisers to forego site-direct buys. Most ad networks today specialize in a niche content area, working with advertisers who wish to have their brand associated with content aligned with their brand category.