How is being president different from being a king?

A president is elected by the people and doe not posess absolute political authority. Also, the president changes every 4 or 8 years. This contributor has made a valid point. To add a bit more, it is assumed that the "president" has indeed been truly an elected one by the citizens. I only mention this as sometimes in a dictatorial nation, the office of president can be a dictator, or lend the office to absolute authority.