This chapter introduces spreadsheet modeling and decision analysis as a field of management science that uses computers, statistics, and mathematics to solve business problems. It discusses how spreadsheet models represent real-world phenomena with mathematical relationships and can help analyze decisions by evaluating potential outcomes. Examples are given of companies that achieved significant cost savings and efficiency gains by developing spreadsheet and other mathematical models to optimize areas like procurement, logistics, inventory management, and operations. The chapter also covers characteristics of models, benefits of modeling approaches, categories of mathematical models, and cognitive biases that can influence decision-making.