The U.S. government consists of three branches: the legislative, executive and judicial branches. Of these, the executive branch is the largest, employing more than four million Americans. Article II of the Constitution details the powers and duties of the executive branch. The president is the chief executive, and if re-elected may serve as many as two four-year terms.

Taking the Lead

Although the three branches are equal, the president is the most powerful single person in the federal government. As commander in chief, the president is the highest authority in the U.S. military. As head of state, the president receives ambassadors and international leaders. The president also has nearly unlimited power to pardon people convicted of federal crimes, although this power doesn't extend to those who've been impeached. The president's broadest power is the power to issue executive orders. Executive orders have the force of law but don't require congressional approval. In times of emergency, executive orders enable a quick response to immediate threats. The president is assisted by the vice president, whose primary responsibility is to be ready to step up if the president is somehow unable to fulfill the duties of the office.

Faithful Execution

The president's oath of office includes the promise to faithfully execute the country's laws -- but this job can't be accomplished by one person alone. The Executive Office of the President includes a number of people, such as the press secretary, who help run the White House on a daily basis. Many of these officials are appointed directly by the president without any input from Congress. Outside the White House, the executive departments, federal commissions and regulatory agencies have the responsibility for administering laws passed by Congress. These agencies and departments have authority to publish detailed rules and regulations in their areas. For example, the Department of Agriculture regulates food production and safety.

Consulting the Cabinet

The president's cabinet includes the heads of the 15 executive departments, and constitutes one of the most important advisory groups in the federal government. Cabinet-level departments include: Agriculture, Commerce, Defense, Education, Energy, Health and Human Services, Homeland Security, Housing and Urban Development, Interior, Justice, Labor, State, Transportation, the Treasury and Veterans' Affairs. These leaders keep the president informed about anything related to their field of responsibility. For example, the secretary of the Department of Energy might advise of a problem with oil supply. The president also may include other officers of the executive branch in the cabinet, such as the vice president or the U.S. trade representative.

Checks on Power

The Constitution places a number of limits on executive power. Perhaps the most important check on executive power comes in the ability to declare war. Although the president is commander in chief of the armed forces, only Congress can officially declare war. The two houses of Congress are responsible for making laws. The president can veto a law passed by Congress, but Congress can override that veto if two-thirds of the members of both houses vote to do so. Any treaties the president negotiates with foreign governments must be ratified by two-thirds of the senate before they become law. Additionally, while the president has the power to appoint a number of executive-branch officials, appointments of cabinet members and directors of many other agencies, such as the Central Intelligence Agency, require senate confirmation.