Managerial economics applies economic theory and analysis to business decision-making. It uses models to predict firm behavior and test those predictions against evidence. While assumptions may not be realistic, the goal is explanatory and predictive power, not descriptive accuracy. Models allow examining how changes like demand or costs impact equilibrium. Managerial economics provides perspective for decision-making but has limitations if assumptions are unrealistic in practice. It is related to but distinct from industrial economics and management science.