These goals are achieved through laws that elected officials to Congress pass, with the approval of the President. The President can veto laws Congress submits and, with a majority vote, Congress can override a presidential veto.
All laws are subject to the interpretation of the courts.
Currently, the US government is dominated by two political parties, the Democrats and the Republicans. These two parties maintain very different platforms and control by either can shift the whole nature of government initiatives. The election cycle is such that every two to four years a major turnover in political power is possible. The amount of money brought in by taxes is directly related to the well being of the economy. The important thing to glean from this civic class review is the intertwined nature of the federal government and the significance of the electoral process.