A general manager usually oversees most or all of the firm's marketing and sales functions as well as the day-to-day operations of the business.
In large companies, many vice presidents will have the title of general manager when they have the full set of responsibility for the function in that particular area of the business and are often titled vice president and general manager.
The general manager may also have responsibility for hiring and firing the head coach of the team.
In fact, many sports teams in the early years of U.S. professional sports were coached by the owner of the team, so in some cases the same individual served as owner, general manager and head coach.
As the amount of money involved in professional sports increased, many prominent players began to hire agents to negotiate contracts on their behalf.