In short, account executives oversee ad campaigns. Advertising agencies are multifaceted, in so far as they create campaigns for clients across a number of mediums -- print, TV, online. Because of this fact there are various people working on different aspects of a single campaign.
While one department within an agency might be creating a series of print ads for a client, another department might be fashioning a series of television ads. Despite this fact all the ads being created need to be getting across the same message, and it's the account executive's job to make sure that's happening.
Put another way, the account executive is there to make sure all the people creating the various components of the campaign are working in a unified manner, and staying on target with the message of the campaign as hammered out by the media planner.
The account executive is also the liaison between the client and the advertising agency. This means that it's up to the account executive to distill the client’s wishes to the creatives at the agency, and vice versa.most agencies look to hire people with a college degree. Account executives, who need to be skilled at working with people and distilling ideas and directions in a clear and concise way, work their way up at advertising agencies. Generally account execs prove their worth by successfully handling accounts and moving on to work on multiple accounts and/or bigger accounts. Above the account executive position is the account manager.