The CEO (Chief Executive Officer) is often but not always also the President of a company. The CEO reports to the Chairman of the Board and board members. The CEO is usually the most important spokesperson for the company, the person who is responsible for quarterly results, and the best paid member of the company.
The CFO (Chief Financial Officer) is sometimes also the company Treasurer and, in many companies, is seen as the second most important person in the company (since managing the quarterly results often depends on an understanding of how to keep the books).
The CIO (Chief Information Officer), a relative newcomer to the ranks of the top executives in a corporation, is responsible for a company's internal information systems, and, especially with the arrival of the Internet, sometimes in charge of the company's
The CTO (Chief Technology Officer), another relatively new arrival to the top executive ranks in many companies, is likely to be seen as the second or third most important person in any technology company. The CTO is responsible for research and development and possibly for new product plans.
The CSO (Chief Security Officer), a recent arrival, is responsible for the security of a company's communications and business systems.
The CCO (Chief Compliance Officer), yet another newcomer, is responsible for ensuring that a company and its employees are in compliance with government regulations and internal policies.