The document discusses the business cycle, which refers to periods of economic expansion and contraction over time. A business cycle consists of expansions, recessions/general contractions, and recoveries/revivals. Key phases include peaks (high points of expansion), troughs (low points of contraction), booms/prosperity, recessions, depressions, and recoveries. During expansions, economic indicators like output, employment and prices increase. Recessions are marked by declines in these indicators. Theories discussed include Keynesian, real business cycle, and political business cycle theories. Government intervention may be needed to control the harmful effects of cycles.