This document discusses interest groups, which are organizations that attempt to influence government decision-making. It notes that interest groups can help address issues like collective action problems. There are different types of interest groups, including economic groups, public interest groups, and think tanks. Lobbyists represent interest groups to government officials. Political action committees raise money to influence elections. Recent Supreme Court rulings have increased the role of money in politics. Interest groups engage in both insider lobbying of Congress as well as outsider efforts to shape public opinion. There is a debate around the representational inequalities and influence that interest groups, especially those with greater resources, may wield.