They are the President and Vice President of the United States. The governor of your State also is a politician. So are your Senator and Representative in the U.S. Congress. The mayor of your town is a politician. So is your elected school board member.
Chief executives are responsible for their organizations.
They work with legislators-people who make laws. They set goals and then decide how to reach them. They hire heads of departments and they make up budgets. They also nominate people for other jobs in government. They get bids from contractors to do work for them, like building schools.