Third party ad serving is the technology that pushes ads out to websites and allows advertisers to track the performance of these ads. Instead of the ads being hosted by the publisher, ads are hosted by a third party from their server. This allows you to track the campaign from the impression served, to click to conversion on your site. Each time the advertisement is called from the ad server, the ad server records that an impression was served. Each time an impression is served; the users who see the impression is issued a cookie that says that person saw an ad for the advertiser. Furthermore we can track the online behaviour of people viewing but not clicking on a display ad, on the premise that they can be influenced to visit the advertiser’s site and complete a conversion (view conversion) as a result of exposure to the ad.