The Executive branch consists of the President of the United States and his delegates. The President is both the head of state and head of government, as well as the commander-in-chief of the military, and the chief diplomat. The President, according to the Constitution, must "take care that the laws be faithfully executed." To carry out this responsibility, he presides over the executive branch of the federal government, a vast organization numbering about 4 million people, including 1 million active-duty military personnel. In addition, the President has important legislative and judicial powers. Within the executive branch itself, the President has broad constitutional powers to manage national affairs and the workings of the federal government, and may issue executive orders to affect internal policies. 

The President may sign or veto legislation passed by Congress. He may be impeached by a majority in the House and removed from office by a two-thirds majority in the Senate for "treason, bribery, or other high crimes and misdemeanors." The President may not dissolve Congress or call special elections, but does have the power to pardon criminals convicted of federal offenses (though not crimes against a state), give executive orders, and (with the consent of the Senate) appoint Supreme Court justices and federal judges.

[ref. Wikipedia - Federal_government_of_the_United_States ]