What is Account Manager?

Legal Definition
An account manager is a person who works for a company and is responsible for the management of sales, and relationships with particular customers. An account manager maintains the company's existing relationships with a client or group of clients, so that they will continue using the company for business. The account manager does not manage the daily running of the account itself. They manage the relationship with the client of the account(s) they are assigned to. Generally, a client will remain with one account manager throughout the duration of hiring the company. Account managers serve as the interface between the customer service and the sales team in a company. They are assigned a company's existing client accounts. The purpose of being assigned particular clients is to create long term relationships with the portfolio of assigned clients. The account manager serves to understand the customer's demands, plan how to meet these demands, and generate sales for the company as a result.

Key accounts provide the most business because they contain a small number of clients which contribute a large portion of the company's sales. According to research, sales from a company's key accounts has increased from 23% in 1975 to 60% currently.
-- Wikipedia
Legal Definition
The day to day manager of a business account. They are the contact point between customer and company. They do customer support, technical support, planning, and enhancing the account. They nurture the customer business relationship.