The president is the country’s chief executive. He heads the executive branch of the government. Millions of people work for that branch. They range from the secretary of defense to the park rangers in national parks. They also include the person who delivers your mail.
In name, the president is in charge of all these workers. In reality, he chooses their bosses. They see that all the departments do their jobs. The executive branch includes the Executive Office, the Office of the Vice President, and the cabinet departments. It also includes more than 100 agencies, boards, commissions, and committees.
Here is a tiny sampling.