A software program that manages and maintains online ads for a Web site or an ad network. This term also refers to the actual server this program resides on. Ad server software is a prime example of an application that was developed solely to support a new business model that emerged from the technology of the Internet. This software tracks and reports Web site usage statistics (traffic), aggregates user information, pieces together bits of data from visitor profiles, and "serves" highly targeted ads. For example, programmers compile and extrapolate data based on a visitor's Web site usage (what you click on). Interest-specific ads can then target you when you visit the same Web site at a later time. In addition, this technology provides the ability to "rotate" online ads so that a user won't see the same ad banner on every revisit to a site.