This report analyzes the concepts of supply and demand, macroeconomic theories, and behavioural economics in contemporary business economics. It discusses the law of demand and its movement, the law of supply, and changes in the supply curve. It also evaluates and compares different macroeconomic theories and explores the impact of behavioural economics on decision making. The report provides insights into the factors affecting demand and supply, inflation, economic growth, and unemployment. It also discusses emerging theories and models of contemporary economics in the 21st century.