The executive branch of the United States is responsible for the implementation and enforcement of the laws passed by the legislative branch as they have been interpreted by the judicial branch. The president is also empowered to sign or veto bills.
Under the executive branch, 15 government agencies headed by presidentially appointed leaders are tasked with the day-by-day implementation of laws. The leaders of these agencies make up the bulk of the president's cabinet. As of 2014, another 50 executive office commissions have presidentially appointed leaders who are not part of the cabinet. There are several other agencies, such as the CIA and EPA, whose leaders are appointed by the president and are directly answerable to that office. In addition to legislation implementation, the president is tasked with several other duties, including the appointment of federal judges and Supreme Court justices, appointing ambassadors, signing off on treaties and making decisions as the commander in chief of the U.S. military.
The vice president, also part of the executive branch, is the president of the senate and has the responsibility of breaking tie votes. This is a rarely exercised responsibility, and the vice president rarely sits in on senate deliberation. Instead, a member of the senate is usually chosen to fulfill his responsibilities.