What is an Ad Server?

An Ad server is a web-based tool where the advertisers or publishers can track the impressions/clicks, and manage their creatives.

There are two types of ad servers:

• Advertiser ad server 
• Publisher ad server

The main functionalities of the ad servers are ad tracking such as the number of impressions served, the number of clicks on the ads and uploading the creatives. This information will be helpful in optimizing the goals based the impressions/clicks etc,.

How ad server works?

Below screenshot, workflow of how ad server works:

For example:

Let's consider, how an ad is displayed on the foxsports.com (publisher website). \

1. When a user visits Forsports.com and publisher website will send a request to the publisher web server.
2. Publisher Web Server responds with HTML code as well as ad code
3. Ad Code sends a request to the publisher ad server to send the relevant ad to be displayed to the user. Along with ad code, the browsers also send some additional information to the publisher ad server such as IP address, Country, device type etc,. Based on the information provided, Publisher ad server will a respond to the relevant to be displayed to the user.
   The main objective of the publisher ad server is to choose relevant advertiser from the group of advertisers.
   
   
4. Once relevant Advertiser is chosen, the browser makes another to request to the advertiser ad server and also send the information about the ad size to be displayed to the user. Then Advertiser ad server responds with the best and relevant ad size to be rendered on the publisher website. Usually, the based which performing good are displayed on the publisher website.
   
   In the below the screenshot, a request is sent to the Adpushup advertiser(advertiser is chosen in Publisher Ad Server) and 728 x 90 displayed to the user.(ad size is chosen in advertiser ad server)
   
   

The relevant ads will be displayed to the users and impressions/clicks are tracked in the Advertiser Ad Servers