This document provides an overview of the structure and key functions of advertising agencies. It discusses the typical departments found in most agencies, including account management, account planning, creative, finance & accounts, media buying, and production. Larger agencies may also have separate human resources, research, web development, traffic, and other departments. Each department's roles and responsibilities are described in 1-2 sentences. The document also briefly profiles three influential figures in the history of advertising - Leo Burnett, David Ogilvy, and William Bernbach - and their impact and style.