This document provides an overview of modern macroeconomics, including the development of classical and Keynesian economic theories. It discusses the essence of classical economists and key aspects of Keynesian economics, such as the concept of equilibrium income oscillating around potential income. The document also introduces the aggregate demand and aggregate supply model and analyzes the slope and shift factors that impact the aggregate demand curve, such as the wealth effect, interest rates, international factors, and fiscal/monetary policies. It concludes with a brief discussion of the aggregate supply curve.