Wherever I have worked the CEO is the person with whom the buck stops. The board answers to the CEO, the CEO to the shareholders.
CEO means Chief Executive Officer which is long hand (American) for the old "Chief Executive", or even more old fashioned "Managing Director".
If you ever got summoned to the MD's office it wasn't so much "tea and no bickies" and "No tea or bickies" and a hefty book stuffed down your trousers!