This chapter introduces some of the main issues that frame the analysis of and the debate on fossil-fuel subsidies and their reforms. It examines the need to monitor and measure fossil-fuel subsidies, including the difficulty of removing them once they are in place. Subsequently, it looks at drivers of fossil-fuel subsidy reform, including international frameworks such as the Sustainable Development Goals, the Paris Summit on Climate Change and the European Green Deal. Next, it discusses two complementary databases developed by the OECD and IEA to track government support to fossil-fuel production and consumption. The chapter ends with reflections on the COVID-19 crisis and its impact on energy markets and fossil-fuel subsidies.