The document provides an overview of the key players in the 2014 European display advertising ecosystem, including sales houses and ad networks that sell advertising for publishers and advertisers; agencies that create and handle advertising campaigns for clients; data providers that collect and sell consumer data; delivery systems and tools that ensure ads are served and measured properly; agency trading desks that buy media inventory; selling and buying solutions that use technology to automate the buying and selling of online ads; and trading solutions and exchanges that connect advertisers and publishers to facilitate ad transactions. It also briefly defines trading desks, agencies, and data providers.