Explore the concept of market structure and how firms compete in this lecture from MIT's Principles of Microeconomics course. Professor Jonathan Gruber introduces fundamental concepts including short-run profit maximization and both short and long-run equilibrium. Gain insights into competitive markets, profit dynamics, and equilibrium conditions that form the foundation of microeconomic theory. This 48-minute lecture is part of MIT's Fall 2023 microeconomics curriculum and covers essential topics for understanding how firms operate under competitive conditions.