Some add 'and CEO' to one to distinguish the person with final executive responsibility. Some organizations prefer President, because they feel it gives more clout to their chief of staff when dealing with the corporate community. Others feel that President should be reserved for the president of the board of directors. If you have an organization, there are responsibilities that must be met to keep things going.
People do the necessary work.
They usually have job position titles. These titles should, in my opinion, be considered completely arbitrary and a matter of convenience and preference. First define the responsibilities of the position. List the set of objectives that spell out what the person is to do. Then, after some thought and discussion, assign the position a title.