Definition: An advertising agency creates, plans and manages all aspects of a client's advertising. Ad agencies can specialize in specific areas, such as interactive advertising, or they can be a full-service agency that creates advertising materials like brochures, catalogs, direct mail, print ads, radio and TV commercials, sales letters, etc.
Most agencies are their own independent company that handle many types of clients and their different advertising needs. Some agencies are in-house agencies, meaning their one and only client is the company that owns them.
Typical employees found at an ad agency include the agency president, creative director, account executives, copywriters, graphic designers and a media director. Some agencies also work with freelance copywriters and/or freelance graphic designers who usually do not work on-site.