The document discusses the role and nature of political parties in the United States. It defines a political party as a group that seeks to control government by winning elections and holding public office. It notes that the two major parties are the Republican and Democratic parties. Political parties nominate candidates, inform and activate supporters on their policy views, and act as a watchdog over the government. While other minor parties exist, the U.S. has essentially a two-party system dominated by Republicans and Democrats due to historical and structural factors.