Prevention, reduction and management of food losses and waste (FLW) have gained an increased global interest since 2011, when the first global FLW report was published by the FAO, and culminated in 2015 with the launch of SDG 12.3. Food insecurity, food systems’ sustainability, and climate change have contributed to the increase in visibility. This chapter reviews a selection of FLW terms and definitions, applied methodologies, and data availability, and identifies challenges such as data comparison and identification of causes. Estimates of the social, economic and environmental values of FLW are useful to generate awareness among food industry members, governments, consumers, civil society and other actors. However, difficulties have been encountered including accepted definitions and terms, gaps in understanding how data on social and cultural variables could be extracted and why these are relevant, lack of incentives to adequately perform economic cost-benefit analyses, and a poor understanding of commodity group specific characteristics.