A social welfare function is a mathematical tool used in economics to evaluate the overall well-being of a society based on the individual utilities of its members. It aggregates the preferences and welfare levels of individuals to determine a collective measure of social welfare. This function helps policymakers assess the impact of different economic policies on the population's happiness and quality of life. Different types of social welfare functions exist, such as utilitarian, which focuses on maximizing total utility, and egalitarian, which emphasizes equal distribution of resources. These functions guide decisions in areas like public policy, income distribution, and resource allocation, aiming to improve societal outcomes.