Operations research is a quantitative approach to decision making based on the scientific method of problem solving. It involves modeling complex real-world situations mathematically and using techniques like linear programming, simulation, and queueing theory to help solve problems and make optimal decisions. Operations research has been used since the 1930s to address issues in areas like logistics, scheduling, and inventory management. It uses a 7-step process of defining problems, considering alternatives, evaluating options, and implementing and evaluating solutions.