The chief operating officer (COO) is the second-in-command of a company, just below the executive director (CEO). As such, everyone, except the CEO, is accountable to the COO eventually, as ideas and plans advance up the scale. The COO usually reports directly to the executive director (CEO) and is considered second in the chain of command. All department heads or other senior managers would report to the COO.
The COO operates as a form of general manager, overseeing the daily operations of a division of the company. The COO is responsible for executing the CEO's vision and for implementing ideas to move the company forward and reduce costs. The COO also holds a senior management position, but has a more refined scope of work than the CEO. Many companies have presidents, vice-presidents, or executives who represent different branches or areas of the company (such as the head of the marketing or human resources department) who report to an operations director.
The operations manager, on the other hand, will not manage any team or manage an operations team. When Larry Ellison, founder and CEO of Oracle, and its chief operating officer, Ray Lane, broke up in 2000, it highlighted how integral the COO is in the chain of command. This classic configuration is no longer found too often, but it illustrates well how important this role is in a company.