system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: the differences between Chairman, Secretary General, President and CEO.
gpt
The Chairman (of the board) is the head of the board of directors. The Board of directors generally doesn't run operations at a company but makes really big, long term decisions, such as choosing the executives that do run the company. The Chairman generally doesn't have any more power per se than any other voting member of the board, except the power to run board meetings.

The Chief Executive Officer is the senior ranking person in an organization, answering only to board. He makes all the decissions of running the company in real time.

The CEO may also be the president and the terms may be interchangeable depending on the business. However, if both terms are used in a company it is likely because the organization has multiple subsidiaries doing different things. In this case the CEO is in charge of the entire umbrella organization and a president runs each individual subsidiary answering to the CEO.

Secretary General (also General Secretary) is a term basically meaning the same thing as a CEO but is favored by multinational, non-profit, and political organizations.