An ad server is a specialised server system that is responsible for storing, managing, distributing and monitoring online advertising campaigns. It acts as a centralised platform that enables advertisers and publishers to efficiently deliver their digital advertising media via various online channels. The ad server holds a variety of ad formats - including banners, video ads, native ads and more - and places them on websites, mobile apps or other digital environments based on a set of defined criteria and algorithms.

An ad server offers numerous advantages for advertisers. These include the ability to control campaigns in real time, precisely address target groups and collect extensive data for performance measurement and optimisation. Publishers, on the other hand, can maximise the utilisation of their advertising space and thus increase their revenue.

Another crucial aspect is performance measurement. The ad server records a range of key figures such as impressions, clicks and conversion rates in order to evaluate the effectiveness of an advertising campaign. This data can then be used to fine-tune the campaign or for strategic planning of future marketing activities.

In the rapidly changing digital advertising landscape, ad servers have become increasingly complex and feature-rich, often integrating with other marketing technologies and offering advanced features such as real-time bidding (RTB), retargeting and personalisation. They are an indispensable tool in the modern digital marketing ecosystem.