An Emissions Trading System (ETS) is a market-based approach used to control pollution by providing economic incentives for reducing emissions of pollutants. Under this system, companies are given a limit on the amount of emissions they can produce. If they reduce their emissions below this limit, they can sell their excess allowances to other companies that are struggling to meet their targets. The goal of an ETS is to encourage businesses to invest in cleaner technologies and practices. By putting a price on carbon emissions, it aims to reduce overall greenhouse gas emissions, contributing to efforts against climate change and promoting sustainability in industries.