Externalities refer to the costs or benefits that affect individuals or society as a whole, which are not reflected in the market price of goods or services. These externalities can be positive, such as when a new technology leads to spillover benefits for other industries, or negative, such as pollution caused by a factory. Research in this area seeks to understand how externalities impact economic decisions, public policy, and overall welfare, and to develop strategies for internalizing external costs and benefits in decision-making processes. This field is important for addressing market failures and promoting efficient resource allocation in economies.