What does ad server mean?

ad server meaning in Law Dictionary

computer system that has advertisements on it and preserves them for internet sites. They monitor and report statistics to simply help identify possible clients.

ad server meaning in Business Dictionary

Computer system which shops, maintains and serves (uploads) advertising banners for one or higher web pages. Ad servers program, track, and report several statistics about readers that are utilized by marketers to customized tailor ads and offers to match different categories of site visitors.