Economics is defined as the systematic study of human behavior under conditions of scarcity, where limited resources must be allocated among competing ends. This chapter establishes the theoretical foundations of the discipline, emphasizing the importance of trade-offs and opportunity costs in decision-making. It surveys prominent subfields of economics, including microeconomics, which focuses on individual agents and market interactions, and macroeconomics, which addresses aggregate functioning such as GDP and inflation. Econometrics provides the essential methodological link between abstract models and empirical data, utilizing tools like time series and panel data to test hypotheses. Other specialized fields, such as development, international, and behavioral economics, offer distinct lenses for analyzing the structural, cross-border, and psychological dimensions of economic life. The chapter specifically articulates the economic relevance of tourism seasonality, illustrating how recurring patterns create structural inefficiencies, labor market volatility, and fiscal challenges for destinations. A conceptual matrix is provided to map how various subfields of economics are applied throughout the book to decode the complexities of seasonal tourism. By grounding the study in these diverse economic perspectives, the chapter prepares the reader to analyze seasonality not just as a fluctuation in visitor numbers, but as a complex economic condition requiring sophisticated policy responses.